Is the scope any good??

[dirty_g]

This is the scope I want http://www.telescopeplanet.co.uk/ViewProdDetails.asp?prod_code=PON05H000017 and this is the scope i already have http://www.telescopeplanet.co.uk/ViewProdDetails.asp?name=Celestron%20Firstscope%20 60%20AZ%20Telescope&prod_code=PON05H000012 is there going to be "that much difference" in what I can see?? If not can you reccomend any others in the same price range (and I mean within £50 of it) that would allow me to see more.

[ozark1]

This is the scope I want http://www.telescopeplanet.co.uk/ViewProdDetails.asp?prod_code=PON05H000017 and this is the scope i already have http://www.telescopeplanet.co.uk/ViewProdDetails.asp?name=Celestron%20Firstscope%20 60%20AZ%20Telescope&prod_code=PON05H000012 is there going to be "that much difference" in what I can see?? If not can you reccomend any others in the same price range (and I mean within £50 of it) that would allow me to see more.

So you propose to move from a 60 mm to a 90 mm telescope. From a purely light gathering perspective you will increase the light available by 2.25 times or just short of 1 magnitude. Moving from say 10.5 to 11.5 will make some difference - the moons of Saturn - Tethys, Dione, Rhea will become quite easy, but objects such as the moons of Mars and Uranus will not be visible. You'll be able to use about 150 - 180 x magnification under best seeing as opposed to 100 - 120 x now.

[ozark1]

However if you want to "see more" at £149, there are other options - Pulsar optical have a 6" Skywatcher dobsonian for £160 (Optical vision do the same for £179).

That telescope will do to just short of the 13th magnitude - more stars, including the Owl Nebula (so all Messiers) and 6 moons round Saturn.

[dirty_g]

really 6" dob for £160?!! sounds like plan!! Messier objects will look good wont they? Planets won't look as good in it compared to a refractor though will they?? Or am I mistaken?

[ozark1]

The dob will be ok to 120x if you can track it. Consider how difficult a manual German mount would be on the refractor at 180x tho - the difference is less than you'd think

[redshifter]

Given a choice between a 90mm refractor and a 6" dob at that price point, I'd take the dob any day. Reasons:

1) At that price point aperature wins IMO
2) The dob mount will be virtually guaranteed to be stable

With 6" of aperature, all the Messier objects should be visible, though many will lack detail.

[Kaptain K]

To play devil's advocate here for a moment:

1) 90mm is a bg step up from 60mm. Not only do you get 2.25 times the light gathering power, but also 1.5 times the resolving power.

2) Even though the 6" dob definitely wins in the aperture department, a properly set up EQ mount makes tracking of objects much easier. Once you have found an object, you only have to track on one axis to keep it in view.

3) Celestron is a known and respected brand of known quality.

[dirty_g]

The dob will be ok to 120x if you can track it. Consider how difficult a manual German mount would be on the refractor at 180x tho - the difference is less than you'd think

I only ever used an AZ mount so have no clue as to how good a EQ mount would be? Is it more steady? Not a clue about these things. I do know that the AZ mount is awful. I align objects with it tighten the knobs and as soon as i tighten them they make the scope dip down and to the left. So centreing an object is impossible with the current AZ mount. Its always in the top right of my scope or sometimes even out of view. Unless I'm lucky that is. So I just view the moon now days and planets like Jupiter. Actually Jupiter is the only planet I have seen so far...... (bah)

[Tog_]

I actually had that EQ90, I think. It looks the same. The advantages of the EQ mount, are that once it's polar aligned, you can keep an object in view, by turning one knob. It will also allow the settign circles to be used to find things you can't see in the finder (in theory) The mount itself will be more stable, mainly because it's bigger and heavier than on the 60.

It will take a little longer to get set up due to the things that need to be attached to the mount, and the need to polar align it, but only about 3 to 5 minutes more, once you get it down.

Drawbacks I had with mine. include a very bright purple halo around Saturn. This is something that can affect any achromatic refrator though. Also, The rod where the counter weight attaches was mounted on a rather weak bit of metal. The mount is Die cast. Once when I was transporting it, the counter wieght hit something and cracked the connetion point. This made it impossible to connect the counter wieght, which you really need to have to use the EQ mount. If you decide to go with this one, Be sure you remove the counterweight before taking the scope down.

Again, this assumes it's the same one I had, and that the design is unchanged.

A 6" dob will have a very fast set up time, but there will be a need to collimate it from time to time. The lower the f number, the more often this will need to be done to ensure good views. I have an f/4.5 dob, and I have to do it once at set up, and again if the temp drops too much. That is in part due to it being a 16" and havign a lot of metal bits to shrink up in the cold.

Either one will be a step up fro your 60mm. I think I would actually go with the Dob. Yes, the 90mm will give a sharper view of the planets, but then, the 6 inch will let you bring in more light and more resolution. The Dob will also be much better on DSO's if you can get to a dark sky. In a city light pollution will be much more noticeable in the dob.

[Maksutov]

I only ever used an AZ mount so have no clue as to how good a EQ mount would be?...There's nothing as good as a well-designed, well-manufactured equatorial mount. When aligned to the celestial pole, once you find an object, then you only need to use the right ascension axis of the mount to track it. Plus if it's adaptable a clock drive on this axis will keep the object in the field for view for hours. It's essential for time-exposure astrophotography.

Of course there are computer-controlled altazimuth mounts that track about the same as an equatorial, but now we're talking $$$.

[ozark1]

There's nothing as good as a well-designed, well-manufactured equatorial mount. When aligned to the celestial pole, once you find an object, then you only need to use the right ascension axis of the mount to track it. Plus if it's adaptable a clock drive on this axis will keep the object in the field for view for hours. It's essential for time-exposure astrophotography.

Of course there are computer-controlled altazimuth mounts that track about the same as an equatorial, but now we're talking $$$.

The big problem here is that we're talking about a cheap Chinese manufactured German equatorial mount without alignment aids or a clock drive. The mount is probably unstable as well. Even with the addition of a clock drive it is unlikely that any satisfactory time-exposure photography could be attempted.

[Kaptain K]

Of course there are computer-controlled altazimuth mounts that track about the same as an equatorial...
But...still can't be used for long exposure imaging, due to field rotation! Of course, you can work around this by stacking many short exposures.

[ozark1]

But...still can't be used for long exposure imaging, due to field rotation! Of course, you can work around this by stacking many short exposures.

Or buy a field derotator - $$$

[Maksutov]

Of course there are computer-controlled altazimuth mounts that track about the same as an equatorial...But...still can't be used for long exposure imaging, due to field rotation! Of course, you can work around this by stacking many short exposures.That's why I wrote "about".

Amazing what things an axis of rotation properly aligned to the Earth's rotational axis can recreate accurately.

[vorblesnak]

There's nothing as good as a well-designed, well-manufactured equatorial mount. When aligned to the celestial pole, once you find an object, then you only need to use the right ascension axis of the mount to track it. Plus if it's adaptable a clock drive on this axis will keep the object in the field for view for hours. It's essential for time-exposure astrophotography.

Of course there are computer-controlled altazimuth mounts that track about the same as an equatorial, but now we're talking $$$.

I tinker with my scopes, probably void the warranty, and I made a simple cheap slow motion attachment for the base plate of my DOB. It is a piece of 3/8th inch all thread mounted on a pivot and held tight against the azimuth mount by a rubber band. Now I can turn the knob slowly and advance or backup the scope to keep an object centered.

For the altitude just use an earl's leg.

OH! I say get the DOB. Lots more light, lots more views. Stable, fast, and if you get into astrophotography and need to track, make a simple Poncet Platform. Or a double arm barn door.

David Davis
Toledo, OR 97391

[dirty_g]

However if you want to "see more" at £149, there are other options - Pulsar optical have a 6" Skywatcher dobsonian for £160 (Optical vision do the same for £179).

That telescope will do to just short of the 13th magnitude - more stars, including the Owl Nebula (so all Messiers) and 6 moons round Saturn.

where is this dob? I can't find one on the net fr that price...

[ozark1]

where is this dob? I can't find one on the net fr that price...

Well

www.sherwoods-photo.com/sky_watcher/skywatcher_fs.html
www.pulsar-optical.co.uk/prod/bushnell/usedexdisplay/voyager6inchdobsonian.html (2nd hand)
www.pulsar-optical.co.uk/prod/telescopes/sky-watcher/dobsonians/skyliner-150.html
www.scientificmirrors.co.uk/Telescopes-binoculars.htm

All of these have 6" dobs under £170

[dirty_g]

Am I to presume that with a 6" Dob I am going to see a heck of a lot more than with a 90mm Refractor?? Considering I would be making a leap from a 60mm Refractor?? I would be interested maiunly in Planets and the moon. But I would also like to see the Ring Nebula and other messiers. I'm not looking for crystal clarity. The view of Jupiter in good conditions from my 60mm Refractor is good enough for me. I presume I would see messiers at about the same quality if I had a 6"dob?

[redshifter]

Based on your criteria above, a 6" dob should serve you very well. There might not be a whole lot of difference in Jupiter compared to your 60mm refractor, but you'll be able to pull in a lot more Messiers with the dob.

[ozark1]

Am I to presume that with a 6" Dob I am going to see a heck of a lot more than with a 90mm Refractor?? Considering I would be making a leap from a 60mm Refractor?? I would be interested maiunly in Planets and the moon. But I would also like to see the Ring Nebula and other messiers. I'm not looking for crystal clarity. The view of Jupiter in good conditions from my 60mm Refractor is good enough for me. I presume I would see messiers at about the same quality if I had a 6"dob?

dirty_g

Your 60 mm refractor collects (60/7)^2 more light than your eye at a dark site. That's 73 x more. Trim it by 10% for light losses, 66 x. 66 x is about 4.5 magnitudes better than your eye, so about 10.5 magnitude is the limit.

A 6" (150 mm) dob, is (150/7)^2 better than the eye - 459 x (trim by 20% for a reflector 367 x) or 6.4 magnitudes better than the eye. The limit is now 12.4 magnitude.

You'll see objects 6 times fainter with the dob than with your 60 mm. The faintest Messier Objects are of 10th magnitude: M108 of visual mag 10.0, M76 and M98 of visual mag 10.1, and M91 of mag 10.2.

[Dave Mitsky]

Just for the record, integrated magnitudes in and of themselves are not a reliable measure of ease of observability. The face-on spiral galaxy M74, which is widely considered to be the most difficult of the Messier objects to log, has an integrated magnitude of 9.4 but a low surface brightness of 14.4 magnitudes per square arcminute. A dark site is a must for good views of this galaxy. Similarly, two even brighter Messier face-on spiral galaxies - M33 (5.7 and 14.2) and M101 (7.9 and 14.8) - usually require dark skies to be seen telescopically. However, the planetary nebula M76, despite its lower integrated magnitude, has a high surface brightness and is not a particularly difficult target.

Dave Mitsky

[dirty_g]

I'm kinda happy. For Xmas im getting a 8" Dob instead! Mwor ha ha. I think that is quite a good scope for me to use. My 60mm for the planets and my Sun observing (I'm getting a filter for it) and the Dob for those Juicy Doubles and Messiers. Anything else the Dob wil be better at resolving? (I presume it will be better at Uranus and Neptune than a 60mm Refractor)

[Dave Mitsky]

Assuming good seeing and proper collimation and cooldown time, the 8" will be superior on all of the planets. However, don't expect Uranus and Neptune to be very exciting through any amateur telescope.

The resolution of your 60mm is only 1.9 (Dawes) and 2.3 (Rayleigh) arc seconds. The resolution of the 8" (203mm) will be markedly better at 0.6 (Dawes) and 0.7 (Rayleigh) arc seconds.

Dave Mitsky

[Kelfazin]

My first scope upgrade was from a 3" reflector to an 8" Dob. I LOVED it. We spent a lot of hours just staring at the Orion Nebula, Saturn, the Ring Nebula, Andromeda Galaxy, etc. Once my brother and I decided to get further into astrophotography I upgraded again to an 8" Meade LX200GPS. I ended up giving the Dob to my cousin since she was just starting to get interested in astronomy (and because i wish somebody had given me an 8" Dob when I was 12 lol) to try and make sure she got hooked for life :)

[Kelfazin]

Assuming good seeing and proper collimation and cooldown time, the 8" will be superior on all of the planets. However, don't expect Uranus and Neptune to be very exciting through any amateur telescope.


I second that. I live in a city with pretty high light pollution and I had a really tough time finding Uranus and Neptune with the dob. I did see them though, but they mainly looked like faint, lightly colored (blue and green) stars. The more popular messiers are fairly easy to find, but depending on your light pollution don't expect a lot of detail in the nebula or galaxies, they mainly look like fuzzy blobs (the Orion Nebula is an exception there, you can see a lot of detail in that even with the pollution. Quite amazing.)

[dirty_g]

I think it would just be ncie to cross the other two Gas Giants off my list. A dob mount doesnt allow you to use co ordinates though does it? But an EQ does??

[Kaptain K]

Orion Intelliscopes Have an object locator computer. It's not a "GoTo" system (no motors), but a "PushTo" system. You enter the object (by name or coordinates) and the computer tells you which way to push the scope. When the arrows go out, the object should be in the field of view.

[ozark1]

I think it would just be ncie to cross the other two Gas Giants off my list. A dob mount doesnt allow you to use co ordinates though does it? But an EQ does??

dirty g

Noone I know of uses setting circles. They are just not worth it - or accurate enough, and if you use a portable mount need setting every time you use the telescope. The prefered method is to star hop across the sky.

Remember even if a DSO is in the field of view, it is useless unless the observer recognises it! Sounds obvious until you are looking for an 11th magnitude fuzzy in the middle of several hundred stars. There are good books to help.

[Dragon Star]

Orion Intelliscopes Have an object locator computer. It's not a "GoTo" system (no motors), but a "PushTo" system. You enter the object (by name or coordinates) and the computer tells you which way to push the scope. When the arrows go out, the object should be in the field of view.

Now that is cool. If I get a scope that will be it. I have heard that the motors can be unrelable in the GoTo systems.

[aurora]

There are good books to help.

These include Turn Left at Orion and Nightwatch (I just saw that there is a new edition of Nightwatch coming out).

Anyway, either of those books will be a big help in star hopping to those dim objects with an 8 inch Dob.

Also, check to see if the Dob comes with a 1x finder (like a Telrad or a red dot finder). Either in addition to or instead of a standard finder scope. That makes getting started a lot easier.

[dirty_g]

I was going to get (dont laugh) astronomy for dummies............

[jouster]

I was going to get (dont laugh) astronomy for dummies............

No reason to laugh. It's a decent overview if you're a beginner. I have found several of the 'Dummies' books to be well wrtten and useful.

[Dave Mitsky]

Terence Dickinson's Nightwatch is generally considered to be the best introductory (amateur) astronomy book.

Dave Mitsky

[dirty_g]

Ment to be getting the 8 inch Dob but I just read about Collimating. Flippin heck that looks fiddly!! Aligning three mirrors is it?? I have a short fuse and I can see myself getting angry at it. Maybe I should of asked for a 90MM REFRACTOR...... oh well. Thanks for the suggestions on books.

[dirty_g]

Well in the end I got a Sky Watcher 150mm parabolic reflector with a motor driven eq mount and a 750 focal length. Does this sound good. What is a parabolic reflctor compared to a normal one? What is different??

[Tog_]

Well in the end I got a Sky Watcher 150mm parabolic reflector with a motor driven eq mount and a 750 focal length. Does this sound good. What is a parabolic reflctor compared to a normal one? What is different??

Parabolic refers to the shape of the curve. Pretty much all Newtonian reflectors will be parabolic. If they were spherical you would end with some really nasty distortion of shape and color.

[dirty_g]

The scope is this one http://www.pulsar-optical.co.uk/prod/telescopes/sky-watcher/newtonianreflectors/explorer150.html let me know if its any good!! :whistle:

[ozark1]

The scope is this one http://www.pulsar-optical.co.uk/prod/telescopes/sky-watcher/newtonianreflectors/explorer150.html let me know if its any good!! :whistle:

Yes it's a good solid Chinese one. It gets good reviews.

[dirty_g]

Chinese? Oh that means its very mass produced and not great craftsmanship then............. (No offence to Chinese people but it is a very mass producing industrialised country)

[ozark1]

Chinese as in not Taiwanese.

95% of all telescopes are either made in China (Synta) or Taiwan (GSO). The Skywatcher brand is good with its quality control and design - similar to Celestron (Chinese). Orion (US) is also Synta. Meade is GSO.

The only volume exceptions are Vixen (Japan) and Orion Optics (UK).


That said - a good Synta (Skywatcher/Celestron/Orion) or GSO (Meade) is far better than other products from the same factory

[dirty_g]

Chinese as in not Taiwanese.

95% of all telescopes are either made in China (Synta) or Taiwan (GSO). The Skywatcher brand is good with its quality control and design - similar to Celestron (Chinese). Orion (US) is also Synta. Meade is GSO.

The only volume exceptions are Vixen (Japan) and Orion Optics (UK).


That said - a good Synta (Skywatcher/Celestron/Orion) or GSO (Meade) is far better than other products from the same factory

Oh!! Great then. You learn something new every day. So the only American made telescopes would be Colorado then? So UK cant make any at all then!!

[JohnW]

Oh!! Great then. You learn something new every day. So the only American made telescopes would be Colorado then? So UK cant make any at all then!!
Among mass-produced telescopes, Meade still makes SCTs and Ritchey-Chretiens in the US. I think Celestron also still makes some scopes here, although this may no longer be the case now that they're Chinese-owned.

A lot of higher-end reflectors and refractors are also manufactured in the US. I think this is unlikely to change any time soon.

[Kaptain K]

Orion says that their Celestron SCTs are still made in USA (current catalog).

[Dave Mitsky]

Just for the record, Meade does not manufacture a true Ritchey-Chretien Cassegrain.

Dave Mitsky

[Kaptain K]

Nor do they claim to.

[Dave Mitsky]

Well, it isn't an "advanced Ritchey-Chretien", either. The Meade design is, in reality, an aplanatic Schmidt-Cassegrain.

Dave Mitsky

[Kaptain K]

I thought they called it a "modified Ritchey-Chretien".

[Dave Mitsky]

I thought they called it a "modified Ritchey-Chretien".

From the Meade home page:

http://www.meade.com/rcx400/index.html

"The dream of owning the ultimate Advanced Ritchey-Chrétien telescope is finally here."

http://www.meade.com/lx200r/index.html

"Meade’s all new LX200R brings Advanced Ritchey-Chrétien optics within reach of aspiring astronomers everywhere. Nearly every observatory reflector in the world is a Ritchey-Chrétien, including NASA’s Hubble Space Telescope. Now you can own what the professionals own."

Meade's cavalier and improper use of the term Ritchey-Chrétien* has resulted in litigation.

http://www.rcopticalsystems.com/FactsofCase.html

http://www.rcopticalsystems.com/FactsofCase01.html

Is this a case of instant karma or what? (Meade sued Celestron not all that long ago.)

When all is said and done, the fact remains that R-C Cassegrains have only two optical surfaces and do not have corrector plates.

Dave Mitsky

From http://www.astronomy.com/asy/default.aspx?c=ss&id=9

Ritchey-Chrétien
This telescope design was developed jointly by American optician George Willis Ritchey (1864 – 1945) and French optical designer Henri Chrétien (1879 – 1956) in the first decade of the 20th century. These two telescope designers found that the lower the amplification factor of the secondary mirror, the flatter the field. The Ritchey-Chrétien system has a secondary mirror that magnifies 2.7x, whereas the Schmidt-Cassegrain design has a 5x secondary. The Ritchey-Chrétien design is coma-free, whereas the Schmidt-Cassegrain is not. Ritchey-Chrétien telescopes have hyperbolic primaries and secondaries that correct for coma; production-type Schmidt-Cassegrains use a spherical primary and secondary and do not correct for coma. Finally, the Ritchey-Chrétien design has two optical surfaces. All Schmidt-Cassegrains have four. Why are Schmidt-Cassegrain telescopes more popular (by far) than Ritchey-Chrétiens? One word: price. A Ritchey-Chrétien telescope is quite costly to produce and, therefore, expensive to buy.

* http://www.rfroyce.com/cassegrains.htm

* http://en.wikipedia.org/wiki/Ritchey-Chr%C3%A9tien_telescope

[Kaptain K]

OK, I stand (sit) corrected. I hope they lose their shirts. Meade has gotten too big for their britches (IMO). The frivolous (and expensive) lawsuit against Celestron being just one example.

On a side note, does anybody know what happened to Celestron's C20 Astrograph?