Framing on a different night with asiair pro

[Chefgage]

Trying to come up with a title that makes sense!

I have a 294mc-pro camera that is controlled from a asiair pro.

The question is let's say I want to add some more images to a project of the horse head nebula. It's been a while and my camera has been rotated a few times. With the asiair I can plate solve to the last image I took but how do I get the orientation correct. 

I suppose I could look at the last image taken and keep rotating the camera until it looks about right but there must be a better way??

[teoria_del_big_bang]

I don't know if there is.
I recently added an automatic rotator and makes life so much easier as the plate solving now also rotates the camera and new images are absolutely spot on to the master image I provide to the plate solver.

But, prior to that what you suggest is basically what I was doing (but tbh I never asked the question if there was an easier method 🙂 ).
All in all it did not take too much messing, I basically took a picture then looked at the two side by side, comparing it to the previous frames or stacked frames, and roughly worked out an angle difference and direction and then manually rotated the camera and took another frame. Maybe, needed to do that 2 or 3 times and it would be close enough that a small crop would take any mis match away.

I know that doesn't help you at all but certainly how I was doing it.

Steve

Edited February 5, 2022 by teoria_del_big_bang

[Ouroboros]

If you plate solve an image with the ASIair it provides the coordinates and the rotation angle. You could make a note of both those on the first night. On the second night you input the coordinates, slew the telescope and then plate solve again. You can then repeatedly adjust the rotation angle and plate solve until the angle is right. If you didn’t note down the coordinates and rotation on the first session you can get this info by uploading your image to various sites like Astrometry or Telescopius to platesolve. 

[Swillis]

Not much use now, but can you put graduations on either side of the part you are rotating? You would then have some sort of reference to get close to where it was. Assuming you note down the 'angke' from the first night. 

[Chefgage]

1 hour ago, Ouroboros said:

If you plate solve an image with the ASIair it provides the coordinates and the rotation angle. You could make a note of both those on the first night. On the second night you input the coordinates, slew the telescope and then plate solve again. You can then repeatedly adjust the rotation angle and plate solve until the angle is right. If you didn’t note down the coordinates and rotation on the first session you can get this info by uploading your image to various sites like Astrometry or Telescopius to platesolve. 

That's sounds like what I am after. I did not realise it gave you an angle. I suppose even if I did not note down the co-ordinates and angle the night before or the session before it would only be a case of platesolving an image from a previous session viewed on the asiair to get that information.

[Ouroboros]

If you’re saying what I think you’re saying, @Chefgage.  I am not  aware that the ASIair can plate solve a previously saved image. If it can I’m happy to be corrected. It would be very useful if it could for the purpose you describe. I know you can do that in other astrophotography control software.  

[Chefgage]

18 hours ago, Ouroboros said:

If you’re saying what I think you’re saying, @Chefgage.  I am not  aware that the ASIair can plate solve a previously saved image. If it can I’m happy to be corrected. It would be very useful if it could for the purpose you describe. I know you can do that in other astrophotography control software.  

I am sure this is the case. I am going to check it later. 

[Chefgage]

On 05/02/2022 at 14:49, Ouroboros said:

If you’re saying what I think you’re saying, @Chefgage.  I am not  aware that the ASIair can plate solve a previously saved image. If it can I’m happy to be corrected. It would be very useful if it could for the purpose you describe. I know you can do that in other astrophotography control software.  

Well I am currently imaging and can now confirm that the asiair can definitely platesolve a previous nights image. Before I went out I deleted all the images off the card bar one. This image was from last week. Then when I had got set up I viewed the image on the asiair via the app and clicked the goto button. The mount then slewed and platesolved to the target based on last week's image.

The only thing it does not do is give you the camera rotation angle of the image from last week. It will only give you the angle from a current image. But going forward this is not a problem. You only have to remembe or right down the angle and use this on the next session of that target.

[Ouroboros]

@Chefgage good to hear. Useful if you’ve left everything set up between sessions. Thanks for finding out about it.  

[ollypenrice]

I just go for 'landscape' or 'portrait' relative to RA and Dec. That makes it dead easy to add data in years to come.

Olly

[Chefgage]

1 hour ago, ollypenrice said:

I just go for 'landscape' or 'portrait' relative to RA and Dec. That makes it dead easy to add data in years to come.

Olly

Yes that makes sense. Only issue I might have is where the target only just fits in the field of view at an angle.

[Rallemikken]

23 minutes ago, Chefgage said:

I just go for 'landscape' or 'portrait' relative to RA and Dec. That makes it dead easy to add data in years to come.

Not with a newtonian. With diffraction spikes wall-to-wall it's impossible to take mulltisessions if you have bright stars in the FOV. You can never reach such an accuracy that your spikes will be crisp and sharp. We'll have to learn to live with it. And then there are the flats. They behave in a special way on newtonians. If possible, I always mount my camera with the pictureframe along or at a straight angle to the telescope tube. That makes me able to reuse TWO sets of flats on most of my work, as long as I use the same camera. On those rare occasions I set my camera at an odd angle, I always take new flats for that session only the next day. I can take multisession shots as long as I don't loosen my camera, and within a limited timeframe. If I don't have clear skies again in a week, it's not worth trying.

[ollypenrice]

11 hours ago, Chefgage said:

Yes that makes sense. Only issue I might have is where the target only just fits in the field of view at an angle.

Sure, but this happens remarkably rarely, I find.  We often see M31 framed on the diagonal but this is usually a shame because, most of the time at telescopic focal lengths, it needs a two panel to fit in it's full glow.

When we 'squeeze things in' we often miss their full glory because, the more data we collect, the bigger they become! That's part of the buzz, of course.

 

[Ouroboros]

For many of us an imaging session is an occasional, often rare activity when opportunity and skies align.  So framing, including optimising angle, is essential to get as good an image as possible within the available time.  We have no idea when we might get another chance. 

[Chefgage]

38 minutes ago, Ouroboros said:

For many of us an imaging session is an occasional, often rare activity when opportunity and skies align.  So framing, including optimising angle, is essential to get as good an image as possible within the available time.  We have no idea when we might get another chance. 

I agree. It's only this year that I have started to add data to previous sessions. 

[ollypenrice]

1 hour ago, Ouroboros said:

For many of us an imaging session is an occasional, often rare activity when opportunity and skies align.  So framing, including optimising angle, is essential to get as good an image as possible within the available time.  We have no idea when we might get another chance. 

Yes, fair point.

Olly