Which scope should I use for astrophotography?

[Brainstorm]

I'm wondering which scope I should attach my camera to for best results. The scopes I have are as follows:

Orion Skyview Deluxe 6" EQ Reflector.

Skywatcher Evostar 90mm Refractor.

Once I get set up with some better gear, I'll be using the refractor as a guidescope, but for now I'm wondering which scope will yield the best results? I have motor drives for both.

[swag72]

You don't say what mount you have for either scope - That will be a major factor with regards astrophotography work.

[rocketandroll]

The answer depends on a few things but in general... the smaller scope will be your best bet.

Both are achromats I believe so you'll get some odd colour separation effects in the stars but you should get some quite pleasing pics out of either.

It sort of really depends what mount you have each on? assuming both are on EQ mounts, it really comes down to tracking accuracy. Generally, with unguided imaging the less load there is on the mount the better the results are likely to be.

For that reason... the smallest scope on the biggest mount should give the best results.

Have a play... get them well polar aligned and see which set up gives you the longest exposures without star trailing.

Try M42 as a good first target... always provides great pictures even from stacks of relatively short subs.

Ben

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[ollypenrice]

The shortest focal length scope on the biggest mount is what you want. (I'm assuming you mean for DS imaging?) As said above, the achromats will give big false colour effects in images. The ideal choice is a small, fast focal ratio apo refractor with field flattener, but have a good go with what you have. The shorter the FL the less critical your guiding has to be.

In fact, for this reason, why not piggyback the camera and use a camera lens for starters? You don't need very accurate tracking for that.

Olly

[Brainstorm]

The Orion Reflector is 153mm x 750 (F4.9) on a "Skyview Deluxe EQ"

The Skywatcher refractor is 90mm x 910mm on an EQ2 (this mount is a lot lighter than the Orion one)

I have motor drives on both mounts

[Brainstorm]

Yes, I'm looking to do deep space stuff.

From what I can make out here, the Orion would be the better option, since it is on a heavier mount and a shorter tube?

I wonder though, what's F4.9 mean on the Orion (and how do I work out what the F stop is on the refractor?). I know what the F stop means in photography; the lower the F stop the bigger the aperture, smaller depth of field and the more light it lets in.. I'm presuming this is the same with a telescope?

[LukeSkywatcher]

The 90mm scope looks like it has a f/l of about 1000mm. This would make it an F11 scope (i think). I have a 90mm scope and the f/l is 1000mm and it is F11...........so i am assuming yours is the same. Great for imaging the moon and planets and some of the bigger DSO's. The shorter tubed scope (F4.9) would be better for imaging many more of the smaller DSO's. The heavier mount is better also for imaging. The 6" scope has a F/L of 750mm.

So basically, the Orion is the scope to use for imaging DSO's.