Which combination of equipment

[Imd]

Hi all,

I have a SW 200p and a SW ST102. I also have an EQ5 and an NEQ6. I was told once that the scope aperture does not matter when imaging all that actually matters is the mount.

I was wondering about what equipment I would take to Kelling, when I realised I might take the lot and image with my ST102/NEQ6 and observe with the 200P/EQ5.

What do you think would be the problems I will encounter if I tried imaging with an ST102 rather then the 200P by increasing the exposure time to compensate?

Thanks for looking

Ian

[Ryan-y]

The apeture isn't important in imaging, it's the focal ratio that is. The lower the f ratio the faster the scope will gather data for a given time. The 200p is f5, and the st102 is f4.9 so that is actually slightly faster.

The st102 is an achromat and that will cause colour artefacts around stars called chromatic aberration so isn't generally seen as suitable for imaging. Having said that, I'd rather be looking through the big reflector at a dark sky site, so Id probably do the same.

In the long run though you will want to be using the 200p, it does have its own problems, but they're easier to get around.

[lensman57]

Hi all,

I have a SW 200p and a SW ST102. I also have an EQ5 and an NEQ6. I was told once that the scope aperture does not matter when imaging all that actually matters is the mount.

I was wondering about what equipment I would take to Kelling, when I realised I might take the lot and image with my ST102/NEQ6 and observe with the 200P/EQ5.

What do you think would be the problems I will encounter if I tried imaging with an ST102 rather then the 200P by increasing the exposure time to compensate?

Thanks for looking

Ian

Hi,

You need a fast focal ratio for imaging particularly in the UK as tranparency and seeing conditions plus light pollution prevents true long exposure astro imaging. Your 200P at f5 is a fast scope, the 102 is a touch faster at F4.9 but it is an achromat, you could image with it but be prepared to be disappointed with the fringing round the stars. The 200 has a focal length of 1000mm, 200mm aperture X F5, so compared to lets say an SW 130 p which is also F5, will give you a narrower FOV. I belleve that NEQ6 is a driven mount, if so it is more than capable of carrying the 200p even for imaging but guiding the 200p is another matter all together. You maybe able to use the 102 as a guide scope piggybacked on top the 200p but at 500 mm focal length it has a narrower FOV than an SW ST80 and a bit tricky to guide.

Regards,

A.G

[ollypenrice]

As above, the ST will have pretty dire false colour with a camera, plus an awful lot of field curvature. It's optically fine for guiding but I'd say it was too big to piggyback on the 200.

Olly

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/22435624_WLMPTM#!i=2277139556&k=FGgG233

[Imd]

I originally bought the ST102 kidding myself I would use it as a guide scope, but I currently use it as a travel scope.

I think from your advice I will take just the 200p/neq6, and may be a will be tempted to buy a little and fast apo from one of the stalls to add to my collection.

Besides with luck there will be someone close by with a massive Dobson like yours Olly

Thanks for your replies.

[Astrosurf]

I use a 200P but on a lighter HEQ5 Pro and it does fine as long as it's not windy! So your HEQ6 would be good. Here's my latest attempt:

I use a finder-guider set-up with PHD which I find excellent. What do you use to guide? The QHY5??

Alexxx

[Pete Presland]

to a certain extent aperture obviously matters, as does having a solid mount. it is all about the balance of the equipment. your NEQ6 and 200p would make a fine imaging combo, with finder-guider and a QHY5 you are sorted.

[Astrosurf]

Just to confuse (sorry!), a little apochromatic refractor is great for nebulae which can be huge. The triplets and above are best but very expensive. But my doublet William Optics Megrez 72mm is lovely, which I got cheap from a friend. Then you need an expensive field flattener if you're using DSLRs and a possible reducer to speed up the scope. I don't use the latter on my Megrez and it's fine. But my Eagle Neb was done on the 200P as it's quite small. I use the 200P for galaxies, smaller DSOs and planets so it's a good all-rounder! But I do love the wide-field of the frac!