New GSO 10 inch RC

[mick pinner]

does it seem to anyone else as it does to me that some equipment manufacturers must be sitting back smiling.
people are buying cheap or affordable gear, call it what you will and then when it doesn't perform up to expectations spend more money to rectify the problem or make excuses that oh well it was cheap.
in the case of the GSO RC, given that some people have pointed out it's shotcomings should not the manufacturer give more information as to it's optical ability so that people know exactly what they are buying.
surely if they are doing the research and manufacturing then they are aware of the problems before they hit the market place.

[Kal (Andrew)]

Paul, my point is not to compare the GSO RC to an APO refractor. Instead I am comparing the GSO RC to a simple newtonian with a coma corrector, which can produce results just as good and at a comparable cost. But a newt with a coma corrector doesn't have the marketing jazz of an RC scope. The main reason why these scopes are popular is because of the $10K+ brand name RC's, and because people have a perception of them being cheap, not because of the results that have been obtained.

If I want a cheap scope that will give me good performance to the corners of a KAF-16803 chip then I'll spend US$1399 (plus eschew and shipping costs) and get a simple SCT with a built in flattener (8" Edge HD). And I know that I won't have to crop corners from the STL11K like peter did, or worry about trying to get flatteners to work to realise the potential of the design.

[Hagar (Doug)]

Paul, I don't know why you bother to justify your purchase each and every time the GSO RC is spoken about. There is a football field of people just sitting on the side lines ready to pounce on your every word.
Looking at the images you have produced with your 8" GSO you have nothing to answer to. If some of the would be experts could produce the same or better results with their big expensive scopes I could see some areas for their comments but to be honest the results all stand in your favour.
By the way. I just ordered an 8" based on your results and the great image scale produced by the scope, not because it is like an expensive scope or brand name display item. Mine will also be used.

[Peter Ward]

Originally Posted by Paul Haese

Just to illustrate my point about bloated stars here are some from the AP gallery.......

Humm...while I thought it wasn't bad at the time...that Corona Australis image is rather dated....not a great example.

[Peter Ward]

Originally Posted by dpastern

The 10" isn't carbon fibre?

Dave

Nope and a little bird tells me the first ones will arive in Oz in the first week of December.

[Paul Haese]

Originally Posted by mick pinner

in the case of the GSO RC, given that some people have pointed out it's shotcomings should not the manufacturer give more information as to it's optical ability so that people know exactly what they are buying.
surely if they are doing the research and manufacturing then they are aware of the problems before they hit the market place.

Yes more information should be made available on the GSO website which is at best amateurism in content. The manufacturers have listened to the reviewers and made the changes to peripheral equipment. The optics I have never found to be problematic, but a spot diagram on the site might be useful.

Originally Posted by Kal

Paul, my point is not to compare the GSO RC to an APO refractor.

I beg to differ, your comment was clearly aimed at saying the stars are bloated on the GSO. I was just pointing out that if everything is equal the pixel size makes a difference to stars even in an AP.

Originally Posted by Hagar

Paul, I don't know why you bother to justify your purchase each and every time the GSO RC is spoken about. There is a football field of people just sitting on the side lines ready to pounce on your every word.
Looking at the images you have produced with your 8" GSO you have nothing to answer to. If some of the would be experts could produce the same or better results with their big expensive scopes I could see some areas for their comments but to be honest the results all stand in your favour.
By the way. I just ordered an 8" based on your results and the great image scale produced by the scope, not because it is like an expensive scope or brand name display item. Mine will also be used.

You are of course right Doug about why I bother and there is a plethora of people willing to take me up on my comments.
I am humbled by your remaining comments. I just keep trying to get better and better at my imaging as you well know. I am glad that my efforts have not gone un-noticed. Thank you very much. These are good scopes and if you want to ring when you get the scope by all means do.

Originally Posted by Peter Ward

Humm...while I thought it wasn't bad at the time...that Corona Australis image is rather dated....not a great example.

I was not intending to insult you Peter, only trying to show that equipment relating to pixel size could be a limiting factor. Your skills have come considerably a long way since then and many of us look to your images now as inspiration and an example of where we should be heading.

[Paul Haese]

Originally Posted by Peter Ward

Nope and a little bird tells me the first ones will arive in Oz in the first week of December.

That might be a problem though. The 8" is very stable and almost never needs to have focus changed during a night once cooled and set. In fact I often find that focus is good from a previous session. Have GSO given an explanation for why they are not using carbon fibre tubes? I was considering getting one but with a ali tube I am less than interested.

[Peter Ward]

Originally Posted by Paul Haese

I was not intending to insult you Peter, .....

I never saw it that way...Absolutely none taken!

[Peter Ward]

Originally Posted by Paul Haese

Have GSO given an explanation for why they are not using carbon fibre tubes? I was considering getting one but with a ali tube I am less than interested.

Two honking great aluminium Losmandy dove rails running from front to rear cells would be my guess...having a low expansion tube would be of little benefit other than a nice look.

Bigger scope, larger mass, more thermal inertia, so a metal tube would also cool a little quicker. BTW I thought the fans were a nice touch

[dpastern (Dave Pastern)]

I thought the idea of the CF tubing was to help with thermal cooling? Larger mirrors take longer to cool, ergo stable cooling/currents etc would be an even greater must with a larger scope? Or am I completely wrong in my logic?

The fans do look pretty cool, I presume a fixed RPM? How are they controlled?

Peter, do you feel that bloated stars are a result of poor focusing/focuser slop/poor optics or just poor CCD/OTA + FL matching? In all honesty, I don't think I've seen a GSO RC based image that looks ultra tight, if you know what I mean? Pinpoint stars...user fault or something more?

Dave

[rat156]

Originally Posted by Kal

Snip...

Their popularity is not driven by their performance. That does not mean that they can't perform well, but I still question why these 300 on the boat to the US will likely sell like hotcakes when the only astrophotography I have seen by them shows bloated stars.

I have bloated stars?

http://www.iceinspace.com.au/forum/s...ad.php?t=52898

Show me a sharper image taken at the same image scale with an amateur scope, then I'll believe you.

The FWHM of the stars in the image was around 2.5" from memory, which is pretty much what the seeing is typically at my place. Like Paul has mentioned the star size is a combination of factors, optical quality of the scope being about third most important as long as its a reasonably good scope.

Cheers
Stuart

[Kal (Andrew)]

Originally Posted by rat156

I have bloated stars?

I was referring to the 10", which as I said, will probably still sell like hotcakes even though the only images I've seen through the scope (granted it was a prototype) which were linked earlier in this thread had bloated stars.

Nice pic BTW.

[Kal (Andrew)]

Originally Posted by dpastern

I thought the idea of the CF tubing was to help with thermal cooling? Larger mirrors take longer to cool, ergo stable cooling/currents etc would be an even greater must with a larger scope? Or am I completely wrong in my logic?

It is around the other way. CF actually insulates, which interferes with cooling on closed tube designs like celestron SCT's, but with the open tube design of the GSO RC it doesn't have an impact on mirror cooling. The advantage of CF is that it can be bought as a zero expansion material, so if you use zero expansion glass to make your mirrors with, you won't have focus shift as the temperature changes through the night.

[Peter Ward]

Originally Posted by dpastern

I thought the idea of the CF tubing was to help with thermal cooling? .....

No, CF is used due its low co-efficient of thermal expansion. Being a composite however, it doesn't conduct heat very well & takes longer to cool.

Originally Posted by dpastern

Peter, do you feel that bloated stars are a result of poor focusing/focuser slop/poor optics or just poor CCD/OTA + FL matching? ....

Dave

Too many variables to know why some images are not great (regardless of the design or make). I wouldn't automatically blame the 'scope when seeing can easily be far more caustic to an image.

[dpastern (Dave Pastern)]

Thanks Kal & Peter. If you don't ask, you don't get answers.

Dave

[gregbradley]

Does it still have a carbon fibre tube?

Greg.

[gregbradley]

Originally Posted by Hagar

Paul, I don't know why you bother to justify your purchase each and every time the GSO RC is spoken about. There is a football field of people just sitting on the side lines ready to pounce on your every word.
Looking at the images you have produced with your 8" GSO you have nothing to answer to. If some of the would be experts could produce the same or better results with their big expensive scopes I could see some areas for their comments but to be honest the results all stand in your favour.
By the way. I just ordered an 8" based on your results and the great image scale produced by the scope, not because it is like an expensive scope or brand name display item. Mine will also be used.

Yes I agree, Pauls images are excellent. The little remaining problem of corner star eolongations could be handled with a flattener. I am not sure that flatteners are that sensitive to different focal lengths (no doubt within limits). For example I use a Tak FS152 flattener designed for a 1200mm APO on my AP140 at 930mm and it works perfectly.
APM sell a generic flattener and Televue have their reducer/flattener.

If you have a flattener for another scope it would make a good experiment to see which fits it.

And take heart this is no criticism of the GSO RC as expensive RCs need flatteners to some degree. A&M RCs apparently really require them.
Just goes to show the formula really is 2 mirrors (a largish secondary) and a corrector/flattener for astrophotography.

Greg.

[Grahame (Grahame)]

Greg: As per Peter's post they are back to an aluminium tube for the 10" (see http://www.atscope.com.au/gsorc10scope.html for picture)

Grahame.

[marki]

Interesting, andrews still has them listed as having a CF tube.

Mark

Originally Posted by Grahame

Greg: As per Peter's post they are back to an aluminium tube for the 10" (see http://www.atscope.com.au/gsorc10scope.html for picture)

Grahame.

[AlexN]

The few guys in the US that got some from NEAF earlier in the year got CF tubes... I dont think they would go to an Aluminium tube after already producing CF tubed models for NEAF? I could be wrong, but it seems unlikely.