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Keiran

Refractor or Reflector?

25 posts in this topic

Hi guys,

I havent been involved in astronomy for very long... about 3 months :D

I think that I have tried almost every hobby know :p and I always try to go for the best I can afford... In equipment for the hobby.

But... I seem to be well and truely hooked on this hobby... most have died out by now, but this one.... I cant get enought of it.

Im starting to hate day light :evil6:

Well to my question.... As you may already know, I have a Skywatcher 200p on a HEQ5... a newly aquired C102... Sony A100... so on and so on!

I have been using the SW200p for imaging for a while now, and bought myself a C102 for guiding, when i get my QHY5...

Reading through threads... Which do you all prefer Newt or Frac' for Imaging?

Which sizes? Mine is quite a big bit of kit, and I am getting results I am really happy with...

But, now I am concidering the kit may be getting a bit heavy for the mount ! What sort of images will I be getting from my C102, If I put an ST80 on it for guiding? Will it compare in amy way to the SW200p...

Will exposures need to be longer because of the reduction in apature?

I think the mount will be fine, but as to taking the setup to a dark site... I think I will be taking the C102 instead :)

Thanks for the replies in advance

Keiran

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The 102 as it is no an APO or Semi APO will have Chromatic Abberations or coloours around objects. I dont think this is the best scope for imaging. Maybe you should look around for a 2nd hand Skywatcher ED80 as loads of folks (including myself) use these for imaging with good results (or in my case average results!)

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well i can safely say from my experience it is much easier imaging with a small refractor then using my 10" schmidt newtonian

its a lot less strain on the mount so tracking errors are minimized, i found it much easier to achieve accurate focus with the refractor and its much easier to handle as well.

You can acheive great results with a reflector, buts its certainly more difficult than using a refractor IMO

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Keiran, the exposure times are dependant on F Ratio not aperture, although bigger aperture means fainter items can be imaged as well better resolution but it is all about trade offs especially with weight/mount loading

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Its strange, I think that most people seem to start off with a newt, because of the price, but then change to a cheap refractor for imaging....

Why do most people use the ST80?

The SW200p and the ST80 are both F5, so what are te advantages and disadvantages, of using the two?

A little bit off to the side, but does anybody know the maximum capacity of the HEQ5, I cant seem to find it on the SW website!

Surely, if a scope can see fainter objects, that would make it better for imaging as you wouldnt need as long exposures to pick out the detail? I dont know?

So what are most people using then... an ST80 as a guide scope, and what scope for imaging... Sticking with refractors.... what would you be looking for, when picking a good imaging frac?

The C102, seems to be fine at seeing stars, so it should be fine for guiding.... but when i looked at jupiter, i did see the colours around it that you were talking about...

Thanks again for your help

Keiran

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As Pete says, f ratio determines exposure time. Focal length determines image scale.

Keep those things in your head first and foremost.

I like imaging with refractors because they are 'plug and play.' They just work. No collimating, no tube rotating, no issues with back focus, no mirror flop, no real cooldown issues and very little dewing. They are small and cheat the wind. Focus snaps in. No diffraction spikes. (I really just don't like them and that's that! I can't help it.)

But a fast Newtonian in a country with limited cloudless time has to have something going for it. Also, as they get bigger refractors have to slow down. By 140mm you are at f7 native and at f5 point something with a very expensive flattener. At some point in the aperture quest a reflector simply becomes inevitable.

I do like the ED80 and were it not for our having the rather expensive FSQ I'd grab one without hesitation. Don't confuse this with the ST80, which as a fast achromat is entirely unsuited to imaging. The colour correction is way short of what an imager needs.

Olly

Edited by ollypenrice

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Thanks olly that was very imformative :D

So theres not much wrong with a newt, other than weight, size, colli... etc as you listed.... and it seems a far bit cheaper...

I was just starting to doubt the equipment i have and am using...

I think in the future i will probably look at getting a Frac' but for now I will stomp on with what I have....

thank you all for clearing things up for me though...

If conditions are perfect, the results from a 8" newt, will they compare to a refractor, or are they in two different leagues...

I think you have to see all of this inperson to fully understand.... This is all such a steep learning curve :p

thanks keiran

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Olly has summed it up nicely about the choices. I really like my refractor but the F4 newt I have is so much quicker in terms of exposures.

For example a 2 min exposure at F4 becomes - 3.5min in a F5.3 Mak Newt and - 5.1min in my 120ED at F6.4 (reducer attached)

Hence if I can get good results from the newt then I can get images so much quicker, I don't mind difraction spikes but the 120ED gives really nice tight stars.

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Kieran,

I have done an awful lot of research with a long term plan to get me into imaging and I was going to gradually build up over the next 12 months to an Equinox ED80 main scope guided by a ST80 on an HEQ6 probably with ATIK 16IC guiding and an ATIK 314L as main camera.

Apart from the weight of the HEQ6, which would future proof me, the two refractors would be easily manageable with my back, I dearly want to add a 10 or 12 inch Dob to the mix for visual too.

Not a cheap entry by any means but from what I have read this imaging setup would give pretty good results as a beginner and not be unwieldy. The SW ED80 Equinox is the shorter focal length than the celestron too.

Why the HEQ6? Well, when my back eventually heals I would have the option of hoisting the DOB tube on it and giving that a good imaging session as well as visual if the fancy took me. Also I think the 6 is more accurate tracking than the 5 and if its carrying weight well below its max that can only help.

Initially my targets would be galaxies and globs, I just love the images I have seen and I am determined to get a big image of the horse head neb close in.

Of course I change my mind daily, but that is the setup I keep coming back to. I think the faster the scope the less tracking errors show up, I could be wrong there but the longer the scope the more likely its harder to get accurate tracking.

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I am using my 200p for imaging at the moment, but its unguided, so im going to use the c102 for guiding and see ho w get on... if i struggle to much with its size, i will concider changing my newt or saving for an additional refractor...

thanks guys

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A short tube frac for imaging would complement the 200p nicely... something between 66-80mm and f6-f7 ish maybe and with a FR these would be around f4-f5 so not too slow either...

Peter...

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Thanks Peter...

I think I will get use to the imaging with the 200p, and make sure I iron out all of the creases out, and then the back end of the year begining of next, i will look at getting a refractor :D

Thanks everybody for you help

Keiran

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'I have done an awful lot of research with a long term plan to get me into imaging and I was going to gradually build up over the next 12 months to an Equinox ED80 main scope guided by a ST80 on an HEQ6 probably with ATIK 16IC guiding and an ATIK 314L as main camera.'

Very nice! More than very nice!!

There is no reason to think the HEQ5 would be less accurate than the HEQ6. The iOptron mount due out soon may also be worth looking at. Obviously the EQ6 has a bigger payload but once your focal length goes beyond about 1.5 metres EQ accuracy for DS is getting marginal - in my view. People do use them at 2 metres.

We have just had two M51 POWs, one refractor and one reflector. I'd have danced all night for either of them!

Olly

Edited by ollypenrice

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Thanks Peter...

I think I will get use to the imaging with the 200p, and make sure I iron out all of the creases out, and then the back end of the year begining of next, i will look at getting a refractor :D

Thanks everybody for you help

Keiran

If you can "iron out the creases" with the 200p then you will find a short focal length frac a doddle...

Peter...

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Imagers do often use ST80's but for the autoguider :D

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I am using my 200p for imaging at the moment, but its unguided... i will concider changing my newt or saving for an additional refractor...

thanks guys

And whats wrong with Unguided, Oh Come on.... Learn to unguide on the 200P, then imaging on the Refractor would be a synch...

I love imaging unguided with my MN190 & considerably heavier then a 200P, but more challenging.. thats why I do a 'Witch Doctor Dance' around my scope before I image. :D:D

Nadeem

Edited by Deneb

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I hope that dosnt come complete with chanting Nadeem, the old neighbours would love that.......lol.

I've had so many ideas for an imaging setup, my first was the same as Mark with the ED80 and a 80mm guide scope.

I've now changed my plans and have two scopes that I can image with, so when I'm imaging with one I guide with the other and vice versa. Different scopes for different strokes.

Now just to save up for that QSI 583WSG........

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I do most of my imaging through what was originally bought as a guidescope... so much so that i added a 3rd OTA ( in the form of a camera telephotolens) as a fulltime guidescope and made sure it was of a suitably "low" quality that it wouldnt be used for anything else...

Peter...

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I hope that dosnt come complete with chanting Nadeem, the old neighbours would love that.......lol.

.......

Yep, thats inc. as well with a small bush in my hands :D

Nadeem..

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But Nadeem... being unguided means that the exposures cant be as long.... Is this not a disadvantage...

At the moment I have no other choice to image unguided, atleast until i have enought money to expand my kit and by a QHY5 for guiding!

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If .... You nail the PA...

If ... You get the balance just right....

If ... Your mount is in good nick....

And ... your Name is Nadeemm...

Then you can get long(ish) exposures unguided...

Otherwise let the Guiding take the strain...

Peter...

Edited by Psychobilly

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Have you Guys never heard of patience... ?

Most of my nebula pics have been done over a period of 3-4 sessions.

Go ahead & join the Puritians :D

Nadeem.

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Just do guiding. We'll get Nadeem on board, fear not. He can still chant. We all chant;

Oh Blank Blank, whtat's wrong now?

Oh Blank Blank, Holy Sow

Blank blank blank

Blank blank blank

blakblankblankblank BLANKBLANKBLANK!

Hope I'm doing a good job of selling imaging...

Olly

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'I have done an awful lot of research with a long term plan to get me into imaging and I was going to gradually build up over the next 12 months to an Equinox ED80 main scope guided by a ST80 on an HEQ6 probably with ATIK 16IC guiding and an ATIK 314L as main camera.'

Very nice! More than very nice!!

There is no reason to think the HEQ5 would be less accurate than the HEQ6. The iOptron mount due out soon may also be worth looking at. Obviously the EQ6 has a bigger payload but once your focal length goes beyond about 1.5 metres EQ accuracy for DS is getting marginal - in my view. People do use them at 2 metres.

Thanks Olly, I am assured I am on the right track and I need to thank you for the heads up in another thread on the kaufmann "universe" book, managed to acquire the 8th edition (current is ninth I believe) from alibirus for £4.72 posted, a blumming bargain, unread with slight shelf marking and with a completely sealed CD. I was surprised at the size and wasn't something I could smuggle in, but the price was a complete winner all round :D looking forward to browsing it when I can. Oh and they only had one listed at that price and I got it, sorry folks.

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