Talk me into something..

[xelasnave]

I want to replace my current imaging scope...a 6 inch MEade sn..
I have thought about a decent refractor but find my leaning is to a celestron 8 inch ota or their 9.25 inch ota...approx $1700 and $2700 respectively.

Firstly should those scopes be disregaurded in favour of a good 4 inch refractor or bigger...if so which one.

AND is it better to go for the 9.25 at an extra $1000
I do like the mak idea but I gather a good one of similar app is pretty expensive.

ANY ideas greatly appreciated.

AND not interested in planetary work just deep sky.

I have an eq6 by the way so it should manage most scopes offered for consideration so please dont tell me get a paramount mount before I get a better scope.

alex

[AlexN]

I'd go the C9.25.

The EQ6 will have no troubles with it. They are light for their size, generally speaking they are held in high regard among imagers for having good/great even the occasional "extraordinary" optics..

They will allow you a good focal length for hunting galaxies, the option of the 6.3 reducer for wider field work... To be honest, I think either the C8 or C9.25 would be great.... But in my opinion, Aperture always wins out... (Check my signature )

[AlexN]

Oh... Mind you, there is a C9.25 + Losmandy GM8 on the forums for sale for $2900ish.... You could buy that, sell the GM8 and have a C9.25 for less than the price of a new C8 OTA....

Its an option...

[rally]

Alex,

Since you used the terms "decent refactor" and "imaging" - how about going for a second hand Takahashi refractor ?

Large flat fields and capable of larger format cameras and DSLRs and able to be upgraded with all sorts of options.

Their 100, 102, FSQ106mm refractors are bearable !
The TOA130mm would ideal !!

They make an ideal imaging platform and depending on your selection would ultimately give you better imaging potential.

Focal length is OK for your intended purpose, maybe get the appropriate 1.6x extender.
They will support eyepiece projection too (with the right adapter).
2" eyepieces can be used for great viewing

Food for thought.

Rally

[robgreaves]

Completely different animals...

What are your imaging aspirations? Wide(er) field or large image scale stuff for small planetaries and galaxies etc.?

Bear in mind that optically, it's always better to Barlow/Powermate up than to reduce down.

Refractors are great - highly versatile, no fuss. A SCT will require constant collimation.

Regards,
Rob

[xelasnave]

Originally Posted by AlexN

I'd go the C9.25.

The EQ6 will have no troubles with it. They are light for their size, generally speaking they are held in high regard among imagers for having good/great even the occasional "extraordinary" optics..

They will allow you a good focal length for hunting galaxies, the option of the 6.3 reducer for wider field work... To be honest, I think either the C8 or C9.25 would be great.... But in my opinion, Aperture always wins out... (Check my signature )

Preaching to the converted eh Alex ..I do like your choice.. what is the drum on colmination?
I saw the add but felt maybe the age went against it... mirrors go off su I believe so I wondered how many light years it had left...but I did think long and hard because as you said it is an opportunity.

alex

[xelasnave]

Originally Posted by rally

Alex,

Since you used the terms "decent refactor" and "imaging" - how about going for a second hand Takahashi refractor ?

Large flat fields and capable of larger format cameras and DSLRs and able to be upgraded with all sorts of options.

Their 100, 102, FSQ106mm refractors are bearable !
The TOA130mm would ideal !!

They make an ideal imaging platform and depending on your selection would ultimately give you better imaging potential.

Focal length is OK for your intended purpose, maybe get the appropriate 1.6x extender.
They will support eyepiece projection too (with the right adapter).
2" eyepieces can be used for great viewing

Food for thought.

Rally

Rally that is not helpful...
that is what I really really want you see and I always have thought images with same are fantastic..so crisp...it is strange I like them so much because I have never seen one up close.

Someone said recently get one and re sell it in a couple of years and the slight drop in price see as rent upon it..that makes a lot of sence to me.

Fortunately or unfortunately depending on the day I have no one to explain my actions to and the dogs dont care so long as they are fed... and happily money is not the problem it was when there is a lady in your life.

I like refractors and love my cheap 150mm but to get a great one I would need a mortgage $30k seems the area... my absolute favorite is the astro physics 150mm... I tried to put my name on their wiating list and they told me I needed to be a resident in the USA... I felt their marketing somewaht elitist ...but clever...tell someone they cant have something and they want it all the more..but not me..they put me right off.

Thanks for taking the time you could sell me one very easily.

alex

[xelasnave]

Originally Posted by robgreaves

Completely different animals...

What are your imaging aspirations? Wide(er) field or large image scale stuff for small planetaries and galaxies etc.?

Bear in mind that optically, it's always better to Barlow/Powermate up than to reduce down.

Refractors are great - highly versatile, no fuss. A SCT will require constant collimation.

Regards,
Rob

Thank you Rob...constant collimation puts me off...I have enough fiddly things to do during set up I will address this aspect before I do anything.

alex

[AlexN]

I am the same, I prefer to buy scopes new... for fear that the previous owner might not be as pedantic as I, and it may not be in the condition I would like it to be...

Collimation of an SCT is laughable... Its SO easy.. I avoided learning newtonian collimation when I had a newt, because it sounded hard... I attempted it finally after 3 months of owning the newt, I gave it a go, failed, tried again, failed, tried again, better but not perfect, tried again (etc etc...) When I got the SCT, I was again cautious to attempt collimation, Even though it clearly needed to be done, because I feared the same troubles I had with the newtonian. I bit the bullet in the 3rd week of owning the C11, and within 5 minutes of starting, the views were (to my eyes) as sharp as my 4" APO refractor.. It was an absolute breeze. now, 6 weeks later, the is still as well collimated as the day I first tweaked it.

It's easy, the scopes hold collimation, sometimes for years if treated with good care....

I think for imaging, an SCT is a great choice... Sure, the refractor will be easier to use, but there really is no substitue for good old fashioned inches!!

[toc (Tim)]

Originally Posted by robgreaves

Completely different animals...

What are your imaging aspirations? Wide(er) field or large image scale stuff for small planetaries and galaxies etc.?

Bear in mind that optically, it's always better to Barlow/Powermate up than to reduce down.

Refractors are great - highly versatile, no fuss. A SCT will require constant collimation.

Regards,
Rob

Actually my C8 seems to hold its collimation very very well. In fact Ive only done it once this year :-) (Then again I dont transport it around that much, so there is no reason why it would get out of alignment)

[xelasnave]

Thats comforting...it will be housed in an observatory (a roll away garden shed) so maybe I should not worry.

It amazes me what I get out of the 6inch so even 8 should be great..

OH I forgot I have tried the 12 inch on the eq6 and have not completed that project... I do mainly unguided even with the 6 inch as I have tweeked the eq6 rather well.. I run it with no greese and only some light machine oil...polished everything somewaht fanatically which certainly made it work well... I have had 10 minute unguided thru the 6invh sn... but the magnification is not that great so I can get away with it... My lastest widefields are all unguided...even the 300 second runs of the LMC was unguided using the 70/300 lens.and widefields at 5o mm I have done 1300 seconds...yes really a dark site only starting to glow after all that time... but it was moist and if dry I could go longer.

I had forgot about the 12 inch work I had done ,,, I know why...I got guiding cameras, then the cat threw up on the lap top and everything was set back..now the shoestring program wont download on the new lap top... got everything else including the box from shoestring to auto guide ...just been doing unguided runs for so long I have overlooked sorting that out.

alex

[xelasnave]

Thanks everyone for the input it has been very helpful...I wont do anything until after xmas just wont have the time but I need to set my goals...now that crazy woman is gone I can get back to it

alex

[AlexN]

I wish i had the Ba... umm. Guts to pull my EQ6 apart and make some modifications... Problem is, even if I had the guts, I wouldnt know where to start to make it better...

[xelasnave]

It is scary but real easy once you have done it once...
What got me was I spent ages trying to unscrew a washer..It would turn about 5 degrees and I turned and turned ...but it was not treaded ... There was a site...Spanish ... so that was interesting.
Have a go ... I cleaned it and bought a little engraving tool and polished and polished... but on the positive I was very impressed with the gear mesh from the wear marks it was a perfect mesh out of the box...
I dont know if the lite oil really works but feel that is does... and given how slow they go lack of greese wont see it seize under high revs...but I think one needs to be able to clean the gears... I found a small spider squashed in the gears which would have translated to PE and one would suspect that dust may get in so being able to clean it is useful.
I used to blue print motor bike two stroke motors and one realises that the factory can leave stuff where is should not be..A single metal filing can stuff tracking really... but internally I was more than impressed with the eq6

alex

alex

alex

[xelasnave]

I set the gear mesh such that they make a noise at fast tracking but that setting was superior as the teeth meshed perfect.

alex

[g__day (Matthew)]

I have a Carbon Fibre C9.25 in a permanent setup. Because of the large temperature differentials I have to re-focus sometimes as often as twice a year. Collimination according to CCD Inspector hasn't moved in the last 6 months.

So maybe its luck of the draw. I've never looked though a high quality refractor and am dying to do so - particularly anything in the 4" - 6" mark. But I expect stars would be smaller and tighter in it. I can't see anything focusing as sharply as a refractor.

Hard choice indeed!

[xelasnave]

Thank you Mat ...you have to refocus as often as that must be a pain..I hope I can get to that stage...that is exciting news I wondered about the carbon fibre I am glad you raised it...frankly with this weather one wonders why bother.

I find it encouraging that you have made such a choice as I respect your opinions very much.

[Rigel003 (Graeme)]

Originally Posted by xelasnave

... my absolute favorite is the astro physics 150mm... I tried to put my name on their wiating list and they told me I needed to be a resident in the USA...

alex

AP sells worldwide so that seems surprising - maybe that was the case long ago. Their lists are so long you'd have no chance anytime soon (10 years) but it's worth signing up online. Doesn't cost anything. There are lots of other, and cheaper, alternatives in premium refractors. I would encourage you to think refractor rather than SCT if your main interest is deep sky imaging. Wide fields and pinpoint star images. SCT images always have larger, bloated stars. I own both but the SCT is used for planetary imaging and the refractor always for deep sky.

[g__day (Matthew)]

Its a trade off isn't it? A refractors costs way more, has shorter focal lengths, less light reach but gives superb focus and tighter stars (someone please check that last point is true and explain technically why!). An SCT is lower cost, so at a same price point has much longer focal length, far more light reach, but even with optimal focus I presume its stars won't be as tight as the refractors?

Is it just a function primarily of focal length that makes an SCT's stars appear more bloated at optimal focus than a refractors? Put another way if you had say a ten inch apo refractor and a ten inch SCT both shoot the same star field onto the same camera (and you didn't expose over the CCDs well depth - so no blooming) - both perfectly focused and both with say a 2.5 metres focal length - would the refractors stars be the same size as the SCTs - slightly less or significantly small and tighter?

[AlexN]

I was just about to say that Matt... maybe its a focal length thing, the bloated stars.

On the other hand, where you said refractors have a shorter FL.. Depending on how much money you wanted to spend, a 9" F/10 TMB APO will decimate a 9.25" SCT for deep sky imaging.. although coolind down a 9" triplet APO might be harder than a 9" SCT.. who knows... (Dietmar knows!!)

If money was no object, I would go a >/= 152mm long focus APO over an SCT. However, Money is an object, and for me, $4k was the limit... So I went with the biggest, meanest SCT my mount/wallet could handle...