So how do you focus your rig?

Recently we have relocated to somewhere with nice clear skies so out comes the old Telescope again

Now with an interest in photography and a telescope comes the inevitable desire to photograph what I am seeing.

Now I have a 8" reflector, an OKish mount with a cheap and nasty tracking motor, a EOS to T-mount adaptor and a eyepiece adaptor for the T-mount.

Thus far the only thing bright enough to focus on with the above set-up is either Venus or the moon and that is using the 20mm eyepiece. In fact I a getting better results mounting my 40D to the telescope and using my 70-200 f/2.8.

So my question is, how does everyone else set-up, and how to you focus the darn thing once the camera is mounted on the scope?

Also tried live view, great for the moon, but not much else.

I use the live view on my 40D zoomed in at 5x or occasionally 10x. Really helps to select the best focus point.

FlyingPete wrote in post #7192835
Recently we have relocated to somewhere with nice clear skies so out comes the old Telescope again

Now with an interest in photography and a telescope comes the inevitable desire to photograph what I am seeing.

Now I have a 8" reflector, an OKish mount with a cheap and nasty tracking motor, a EOS to T-mount adaptor and a eyepiece adaptor for the T-mount.

Thus far the only thing bright enough to focus on with the above set-up is either Venus or the moon and that is using the 20mm eyepiece. In fact I a getting better results mounting my 40D to the telescope and using my 70-200 f/2.8.

So my question is, how does everyone else set-up, and how to you focus the darn thing once the camera is mounted on the scope?

Also tried live view, great for the moon, but not much else.

Is your reflector either a Newtonian or a Schmidt Cassegrain?

There are several inexpensive ways including using a Hartmann Mask and this new mask below that's the latest and greatest. Both of these can be made at home(see FREE templates at link). A test shot or two and some minor focus tweeks is all that is needed.:
http://www.focus-mask.com/

I use a Stellar Technologies Stilletto focus aid. It hasn't let me down yet but it's not a Free item. Works especially well on refractors.

On a DSLR I tend to use the viewfinder for rough focus and then find a brightish star near my target and take shots about 5 to 10 seconds long into Maxim DL and monitor the FWHM value. Takes about 10 minutes but seems a lot longer when you are doing it.

Nighthound wrote in post #7195355
Is your reflector either a Newtonian or a Schmidt Cassegrain?

There are several inexpensive ways including using a Hartmann Mask and this new mask below that's the latest and greatest. Both of these can be made at home(see FREE templates at link). A test shot or two and some minor focus tweeks is all that is needed.:
http://www.focus-mask.com/

I use a Stellar Technologies Stilletto focus aid. It hasn't let me down yet but it's not a Free item. Works especially well on refractors.

It is a Newtonian 130mm f/8.

That mask is pretty clever, plays on the effect you get when the scope is way out of focus, you see the bars holding the middle piece (excuse my pseudo technical terms!) in place.

Will give that a go.

chris.bailey wrote in post #7196016
On a DSLR I tend to use the viewfinder for rough focus and then find a brightish star near my target and take shots about 5 to 10 seconds long into Maxim DL and monitor the FWHM value. Takes about 10 minutes but seems a lot longer when you are doing it.

Hmmm a task requiring more patience, seems I will need some more to get the good results!

I find through my scopes I can pick up quite a few stars on Live View...certainly ones far dimmer than Venus. It makes focussing a doddle and usually takes under a minute.

Before, when I didn't have Live View, I would focus as best I could through the viewfinder, then take a 5 or 6 second shot. I'd adjust the focus in one direction by a fraction, then take another 5 or 6 second shot. I'd then bring up the shots on the display, zoom in a fair bit, then flick between the images, comparing them to find which is best. If the first was best I'd focus back a fraction, then back a fraction more, and take another shot, comparing the first and third. Basically did that over and over until I had a satisfactory result. Never took more than a few minutes.

Of course, a mask emphasises the bad focus, making it easier to get it spot on. But the process of taking and comparing images would still apply if you haven't got Live View or a bright enough star.

FlyingPete wrote in post #7196148
It is a Newtonian 130mm f/8.

That mask is pretty clever, plays on the effect you get when the scope is way out of focus, you see the bars holding the middle piece (excuse my pseudo technical terms!) in place.

Will give that a go.

The advantage of a Newt is that you have spider vanes to create star spikes. The spikes make it easier to assess focus as long as you can magnify the smallest star capable of creating a spike. Critical focus requires that you evaluate the smallest stars, unfortunately the smallest stars won't project spikes. So to achieve consistent critical focus, you'd be best served to use a mask or preview test shots on a laptop so that you can magnify the image enough to see those tiny stars clearly. I got tired of the test shot routine and went with the Stiletto, it's dead on 99.0% of the time. The other 1% is usually operator error.

Your Newt being f/8 is going o be a challenge for long exposure work. Also, do you have a coma corrector?

Nighthound wrote in post #7197002
The advantage of a Newt is that you have spider vanes to create star spikes. The spikes make it easier to assess focus as long as you can magnify the smallest star capable of creating a spike. Critical focus requires that you evaluate the smallest stars, unfortunately the smallest stars won't project spikes. So to achieve consistent critical focus, you'd be best served to use a mask or preview test shots on a laptop so that you can magnify the image enough to see those tiny stars clearly. I got tired of the test shot routine and went with the Stiletto, it's dead on 99.0% of the time. The other 1% is usually operator error.

Your Newt being f/8 is going o be a challenge for long exposure work. Also, do you have a coma corrector?

No I don't have a coma corrector, and I can see the effect of not having one whilst looking through my 20mm eyepiece, haven't got a descent camera shot yet so don't know how much of a problem it will be.

Stiletto looks good, but I don't have the spare $$$ to ship one down here, will see if anyone does them locally first.

Thanks for the help!