Getting DSLR into focus

[Marky1973]

Finally got some clear skies and popped out with my motorised EQ3-2, Canon 1100d and Starwave 70ED. Now, I know this isn't the best set-up in the world, but I want to try my hand at imaging and see if I can get anything at all before I go crazy.

Anyway, didn't really work out. DSS stacked everything fine, but the finished image looked no better than the original RAW files. I took 25 30 sec LIGHT/DARK/BIAS frames just for fun, but there was very little detail that I could make appear in GIMP of Andromeda. Now, that is just down to practice, I realise that. However, part of it was probably down to not quite being able to get the Canon in focus even at the very farthest stretch of the focussing tube - i really was just testing the rig to see if it would track.

So I presume I need an extender.

The place if got the scope from suggested that I would need an M48 40mm extender. I have the T-Ring already, so presume the two can be coupled and used in the scope. Here comes the stupid question. I presume that the idea is to place the extender in the focuser and adjust it back so you can get the camera in focus....so a 40mm will be better than, say 20mm, as it will give you more room to play with. Or are they used in a different way.

It probably is a stupid question, but I want to make sure I think know what I need to buy! ;-)

After all, it is clearly going to be a steep learning curve for me, seeing as it was only when I was packing everything up that I realised I had not attached the counterweights, which probably didn't help!

I reckon if I can get the weights on, the focussing right and properly polar align, then I may be able to go to 60 sec subs and possibly over?

Sorry, I think I am rambling.... I was just really wondering if I understood the way an extender was used, so I could get the 40mm extender without any worry!

Cheers

[PorkyB]

I use a 70ED and 1100D.  It's a great little scope and I have had some good results with it.  I use the Altair Astro 1x field flattener, which screws on to the T-ring, so it sits on the front of the camera like a lens.  With this fitted the camera fits directly onto the scope and achieves focus with the focusser around 3cm out.  I can lock the focusser when I have camera focus and then swap back to the diagonal and eyepiece, with a bit of adjustment (sliding the eyepiece out a little bit) I can have the eyepiece parfocal with the camera.

I realise this is a lot more money than a simple extension tube (it's £75) but the improved image quality and convenience make it worth it to me.

[oldpink]

TBH Andromeda isn't a great target, yes its big but even with a 200p on a HEQ6 I struggle to get anything decent from Andromeda even at 3 - 5min exposures

as to getting focus I have no knowledge of your scope but extension tubes  can be a must but you have to get the correct one
if its too sort or long it will not solve your focus issue, you need to find the exact distance from your scope to the camera sensor or you will never get it right

AP isnt a cheap hobby, to do it with any decent results you need to spend a lot of time and money
30s exposures won't give you any great detail unless its a very bright object 

[PorkyB]

30s exposures won't give you any great detail unless its a very bright object 

The 70ED is small and light, with careful balancing and polar alignment you should be able to get 2 or 3 minute subs, even on a lightweight mount.  This I the best I have managed with the 70ED and 1100D, admittedly on the slightly more sturdy EQ5.  (15x180 seconds plus bias).

Andromeda Galaxy by porkyb, on Flickr

Sky conditions play a large part  when imaging M31 and all galaxies.  This was a nice clear night and I was 15 miles out of town, but still in the light-polluted West Midlands. I have tried on less good nights and got nothing but the core.

[Astrosurf]

I have a Megrez 72mm frac and use a field flattener. It's excellent. As has been said, AP  is expensive! I don't know about the 40mm extension tube but maybe have a go as it'll be cheaper.

Try imaging the Moon to start with as it's very bright and you can see what you're doing! Then, when sorted, have a go at brighter DSOs like globular clusters. Then go fainter when you're more confident.

Alexxx

[Alien 13]

The less you have to move the focusser tube out the better i would have thought a 2" extender would be a good option.

Alan

[Marky1973]

Cheers all! I realise Andromeda was not the best choice, but I was limited to time and its and easy one for me to find in my location! I really just wanted to test focusing too and see what i needed to do before I start trying to do more serious stuff. Although, to be honest, even the awful stuff I got was quite exciting! Re-reading "every photon" again as well!

Porkyb - is that this one? https://www.altairastro.com/product.php?productid=16203&cat=291&page=1 and that is all you use. Interesting that you say the focusser only comes out to 3cm as I was only just starting to reach focus with the barrel completely out, so it obviously has a pretty beneficial effect. And love the image. I did just get the core last night but, as I said, wasn't expecting much - once I get myself sorted and know what I am doing I'll get myself out to a darker site and have a go.

Thanks oldpink - I guess the recommended 40mm tube is probably the one to go for then, if not the field flattener.

Hi Alexxx - have done the moon a few times with my dob, not tracking or anything flash, so perhaps I need to try some clusters as you say - hercules is easy to find at the moment, so maybe that will be a cluster to start with - the altair astro tube was about £40 I think, so the field flattener, if it improves things that much might not be a bad investment.

Thanks Alan - need to do some more reading and see what costs/options there are, or decide on the flattener!

Thanks again everyone. Hope I will be able to get an image worth posting soon.

I'l have another go on the clear night in November! ;-) 

[Astrosurf]

Let us know how you get on.

[Marky1973]

Thanks Alexxx.

Gone with the recommended 40mm extender from Altair for know as I know it should work, and funds are drying up! (I also need/want a polar scope and a dovetail bar, so having to be prudent!) If things go well, then the flattener might be an idea for a Christmas present! ;-)

[PorkyB]

is that this one? https://www.altairastro.com/product.php?productid=16203&cat=291&page=1 and that is all you use. 

Yes, that's the one. 

Camera - T-ring - flattener - scope.