Maksutov-Cass versus Newtonian

Folks - can anyone give me a succint description of the major differences (benefits & drawbacks) between a Mak-Cass and Newt for use in astrophotography?

I know prices are different but that's really it. Irrespectyive of price, which would be the better performer?

Pretty pictures are not required (so coma-free stars to the edge of the field are not a neccessity). I'd be interested in optical performance, ease of collimation, cool-down times, structural stabilty, ease of maintenenace etc etc.

Cheers

Dave

Dave without going into two much detail the main differences are;

Maksutovs are generally very long focal lenghts f/10 - f/15 they are generally well corrected right out to the edge. Cool down times are longer because there's a lot more glass in a mak. The front corrector plate is very thick (compared to an SCT). Larger maks usually have a fixed mirror and employ a rear movable focusser. Smaller maks use a movable mirror liek SCTs.

Collimation would be more tricky, but by design it's harder for it to go out of alignment in the first place. I have a 5" mak and it is lovely. It has never needed collimation despited falling on the floor one time. It would be great for scientific phototography, but too long for pretty picture photos. Contrast is better than a newt because of the lack of a spider.

Over all and knowing what you are interested in doing, I'd say go with a mak over a newtonian. But if the choice were makvs SCT I'd say it would be a closer call.

Just an addendum. Of course a newtonian will give you far better bang for buck and allow you to buy far more aperture, hence the possibility to image those faint quasars etc!

Hi Dave.
You don't say what objects you will be imaging and for what!.

Anyway some general points:
1. Maks are slower.
2. Coma can be an issue even going beyond pretty pictures (could
use a Photo Coma corrector in a Newtonian)
3. Maks have less maintenance.
4. Maks more difficult to collimate, but (a good one) is less likely to go out of collimation in first place.
5. Optical Performance on larger/lower cost Maks are not very good.
6. Very good maks are expensive.
7. Maks cool down are longer than Newtonians of similar aperture, but
you would probably want a larger aperture in a Newtonian.

John

I wouldn't rule out the issue of coma Dave, especially if you decide to get a large format chip. If the scope is of a design which has alot of coma, then this will show up on your image. To take scientific readings involving photometry or astrometry could become difficult with an elongated star on your image.

OK - I said price didn't matter but I guess it does when weighing up pros and cons

The options I have are:

Mak Cass 14" 6.6K
Mak-Cass 16" 15K

Newt 16" 4.6K
Newt 20" 12K

The 16" Newt looks the best bang for the buck and its a huge jump to the 20". If I went down this route, I'd get a Wynne Corrector which will reduce/eliminate coma. I know what you mean Michael - I guess the minimum requirement would be coma-free to 75% or so of the FOV. Any object in the elongated star region is probably of no interest to me. Of course, I still need to do the research on the Wynne Corrector...

The purpose of the imaging system will be for astrometry and photometry so the subject will usually be in the centre of the FOV. Of course, with photometry, there will also (hopefully) be comparison stars in the image too that will need to be measured. But, hopefully, they will also be close to the centre of the FOV or at least in the 75% area mentioned above.

Dave G - funnily enough, the Orion Optics Mak-Cass has a spider... Out of interest, which has the larger % obstruction - the Mak-Cass or the Newt?

Cooldown is probably not that much of an issue since the OTA will be outside permanently, so it shouldn't have to cool down by a large margin, if at all.

Thanks for the feedback so far.

Dave