Framing with a H-Alpha filter

[Bonamy]

I was making the most of the clear skies last night targeting the Elephant's Trunk with my recently modified Canon 60D with a clip in H-Alpha filter.

Does anyone have any tips for framing without a GOTO mount when using a filter in a DSLR?

It took me an hour to get the focus and framing to the point where I was happy. I even resorted to plate solving the previews to help zero in (and I'm only at 300mm). I'm sure second time round I'll be better, but it was difficult to work out how much adjustment was required. Just so difficult to see in preview and matching up with the sky.

Anyway, very enjoyable night. First time guiding, and that all went well (although still some star trailing, so plenty of room for improvement).

Canon 60D (modified) Red Dot finder on hot shoe
Sigma 70-300mm 
Clip in 12nm H-Alpha filter
Star Adventurer
ZWO Mini with ASI120 mini scope
PHD2 / Backyard EOS / DSS / Photoshop
ISO 800, 64x300s subs, 20 Darks, 30 Flats


 

 

[Knight of Clear Skies]

Yes, it can be tricky if you can't see the target. In the past I've done this by bumping the ISO up to maximum and taking short exposures, then fiddling.

[Bonamy]

12 minutes ago, Knight of Clear Skies said:

Yes, it can be tricky if you can't see the target. In the past I've done this by bumping the ISO up to maximum and taking short exposures, then fiddling.

Thank you.

That would make sense. I didn't seem to be able to go over ISO 6400, so think I'll have a dig around the camera settings, I thought it could do more.

I did consider taking the filter out, framing up, and then putting the filter back, but obviously there is a risk of moving the mount.

[Altair8389]

I can see the Elephant trunk ! Good attempt. I think you may need to just find a bright star with a Bahtimov mask...centre the spikes. Then move to your target, being careful not to move the polar alignment out...You may have to check polar alignment again after you move to your target.

So focus your camera with the H-alpha filter on a bright star with a Bahtimov mask, and then tape the focus ring with a tape. Then move to your target, re-check polar alignment and go again on your target.  Have you thought about using Astrophotography tool ? I think you can do plate solving in that and that would help you find your target and frame it more accurately.

 

[Chefgage]

The only thing I can suggest is when I am using my Ha filter and star adventurer is to up the iso as high as you can go and still see the image after taking a short exposure. But I agree it can be tricky.

[Bonamy]

9 hours ago, Altair8389 said:

Have you thought about using Astrophotography tool ?

Thank you for the tips. I've just had a look, and this tool looks impressive. I'll try it out in place of Backyard EOS.

[Bonamy]

8 hours ago, Chefgage said:

The only thing I can suggest is when I am using my Ha filter and star adventurer is to up the iso as high as you can go and still see the image after taking a short exposure. But I agree it can be tricky.

I'll push the ISO and focus on a bright star before framing. Thank you.

One thought occurred to me with the polar alignment is that I wasn't locking down the allen keys on the Star Adventurer horizontal alignment clamp. Do you tighten these after alignment? 

[Chefgage]

4 hours ago, Bonamy said:

I'll push the ISO and focus on a bright star before framing. Thank you.

One thought occurred to me with the polar alignment is that I wasn't locking down the allen keys on the Star Adventurer horizontal alignment clamp. Do you tighten these after alignment? 

If your talking about the Allen bolts that go between the white and green part of the base of the mount then no these should not be tightened. They allow the mount to move horizontally by turning the left and right thumb screws. The Allen bolts if i remember are on teflon washers which allow the mount to move when polar aligning.

The only thing I do is gently nip up the left and right thumbscrews after I am happy with the polar alignment.

Edited March 25, 2021 by Chefgage

[Bonamy]

Yup, these were the ones I was thinking. So all good, I won't clamp them down.

Thank you.