asiair plus Polar aligning with ASIair Plus

[Blaired79]

Hi all,

I'm looking for any advice or guidance for the following.  

am really new to Astrophotography and to help make it easier I have bought ASIair Plus and Sky Watcher Sky Adventurer GTi.  Last night was my first attempt to Polar Align.

I get this error Warning: FOV out of range (0.2°-33°) This image may not be solved (screenshot attached)

I've read some posts that mention that certain cameras aren't suitable for PA, I've seen mentions around the degrees...  I have a Canon EOS 450D and I'm not sure where to find out this information.  Any help would be greatly appreciated.

 

Mike

[900SL]

What lens focal length have you input into the ASI? 

Are you pointing at Polaris? 

Edited Thursday at 13:39 by 900SL

[Elp]

As per above, it's likely the lens FL which is the issue, I've only ever had that warning once in four years of using the air, I was using a 24mm lens at the time, it also happened with a 35mm. Plate solving can be brute forced but don't expect it to work every time.

[Stickey]

This is the Field of View trap for the unwary astronomer. There are some huge targets and some tiny ones and no one telescope/camera combination will show them all equally well. 

You can find the FoV of any particular combination from several sites,  this is 1 of them - https://astronomy.tools/calculators/field_of_view/?origin=serp_auto

FWIW,  the bigger the camera sensor, the bigger the FoV and a Canon 450D is an APS-C sized sensor, which is quite large. 

So, you need either a smaller camera sensor or a longer f.l. telescope. 

Hope that's helped. 

Edited Thursday at 14:17 by Stickey

[Elp]

With the asiair is doesn't matter what size the sensor is, the focal length of the optics will remain consistent +/- a few mm and it will plate solve accordingly. Either the user inputs 0 for the main scope focal length if they're unsure, or they can input a near enough value, once an image is taken by the main camera and plate solves the air will automatically input the focal length it's calculated. It doesn't matter if you change sensor size in between, the focal length will remain fairly consistent when it solves.

 

Edited Thursday at 14:27 by Elp

[Ouroboros]

Yep, it not knowing the focal length is almost certainly the problem. I notice it’s 0mm in the screen shot.

Funnily enough I had this problem the other night because I’d swapped telescopes and hadn’t changed the focal length set in the air.  Had me scratching my head for a bit until the penny dropped ….. and I think I know what I’m doing ha ha! 🤣 

[900SL]

A few more possibilities:

Too short an exposure

Out of focus

Lens cap on

wrong hemisphere / location set

wrong focal length set

Too short/too long focal length (Asi has limits on FOV)

All sky polar align/advanced PA options checked

Database error in AAP

Not polar aligned.. stars trailing

 

Can you see stars clear and sharp on test exposure?

 

[StevieDvd]

Entering the focal length as zero is a good start if you have the correct camera selected. The ASIAir will use those to calculate the FOV as long as it can see a decently focused/exposed image.

Check your camera selection for main camera and make sure you can see a few stars in the PA screen.  Exposure needs to be around 2-5 seconds but on a DSLR you may need to select an appropriate ISO speed for that to work.

 

[M40]

Another thing that might be worth trying; before entering the pa routine, in preview, goto a target, center and focus it, then select plate solve button. If plate solve fails it will be a setting, too cloudy or not enough stars. If solve fails and assuming it's not cloudy, mess around with the aperture, speed and iso. Hopefully it will eventually solve. Only when you can get it to solve, goto the home position then enter the pa routine. Hope it helps.

All the best.

[Blaired79]

3 hours ago, 900SL said:

What lens focal length have you input into the ASI? 

Are you pointing at Polaris? 

 

Don’t laugh but I think so. I’ve put the mount due north and set the latitude to my location. 
 

I had the focal length set to 0 and after some research I found that it shouldn’t matter too much but after looking up this I can set this now. 

Edited Thursday at 16:48 by Blaired79

[Blaired79]

2 hours ago, Ouroboros said:

Yep, it not knowing the focal length is almost certainly the problem. I notice it’s 0mm in the screen shot.

Funnily enough I had this problem the other night because I’d swapped telescopes and hadn’t changed the focal length set in the air.  Had me scratching my head for a bit until the penny dropped ….. and I think I know what I’m doing ha ha! 🤣 

Am I right in thinking that my focal length will be determined by my lense I attach? For example I have one lens that can range from 18 to 55mm

[Blaired79]

21 minutes ago, M40 said:

Another thing that might be worth trying; before entering the pa routine, in preview, goto a target, center and focus it, then select plate solve button. If plate solve fails it will be a setting, too cloudy or not enough stars. If solve fails and assuming it's not cloudy, mess around with the aperture, speed and iso. Hopefully it will eventually solve. Only when you can get it to solve, goto the home position then enter the pa routine. Hope it helps.

All the best.

Thanks I’ll try this tonight. I think I recall seeing the f value on the dslr as being really high despite having initially set it to 5.6. 
 

From memory it was finding 32 stars.  ISO set at 800, I did tinker with the exposures from 5 seconds to 1000

[900SL]

50 minutes ago, Blaired79 said:

 

Don’t laugh but I think so. I’ve put the mount due north and set the latitude to my location. 
 

I had the focal length set to 0 and after some research I found that it shouldn’t matter too much but after looking up this I can set this now. 

What focal length lens are you using, and what is the widest aperture? (F stop)

[Blaired79]

18mm at 3.5

[Ouroboros]

1 hour ago, Blaired79 said:

Am I right in thinking that my focal length will be determined by my lense I attach? For example I have one lens that can range from 18 to 55mm

  I think it will  if you do a plate solve.  

[Blaired79]

1 hour ago, Ouroboros said:

  I think it will  if you do a plate solve.  

Plate solving fails, it keeps trying but always fails. I’ve given up for tonight as the lens is misting up but I have a dew heater arriving tomorrow which I hope will do the trick. 
 

I’ll try solving again tomorrow and take some screen shots.

[Ouroboros]

Try guessing the approx focal length. 

[Elp]

1 hour ago, Blaired79 said:

18mm at 3.5

See my previous comment, 18mm might be way too wide for the air to solve (hence your previous error), at f3.5 with a variable zoom lens your stars may also have coma or be distorted so it can't solve, in such case it'll either attempt to solve for a very long time or it'll say solving failed.

[Blaired79]

OK I think the penny is finally dropping here and as you can probably all tell, I am completely new to new and don't have a clue (running before I can walk)

My understanding is that the FOV is too large on the current focal length I was using between 18mm and 55mm.  The ASIAIR needs a minimum FOV of 0.2° x 0.2° and maximum FOV of 33° x 33° to be able to plate solve.

I used the Canon calculator and if my focal length is 100 mm or more I should be OK......

 

[Elp]

You need to also review your star shapes and check for noise in the previews as that can also cause plate solving to fail.

With my airs and apsc I've used down to a  24mm lens, with full frame down to 50mm.

[900SL]

Just as a bonus, If you are shooting at 18mm forget accurate PA, your FOV is so wide you can ensure good tracking using just a compass and inclinometer

I recently took photos of the Atlas comet at 135mm focal length and 30s exposures doing this. Using 20mm Nikon lens I just eyeball it

[MalcolmP]

18 hours ago, Blaired79 said:

From memory it was finding 32 stars. 

Hi, I am a bit late to the party and no experience of ASIair so this may be of no help ! 32 is not a lot  
To test a pic for solvability has anyone mentioned Astrometry.net ? https://nova.astrometry.net  It gives lots of info about a solved pic  which may be of use in setting the right info into asiair.

 

Edited Friday at 11:54 by MalcolmP

[Blaired79]

31 minutes ago, MalcolmP said:

Hi, I am a bit late to the party and no experience of ASIair so this may be of no help ! 32 is not a lot  
To test a pic for solvability has anyone mentioned Astrometry.net ? https://nova.astrometry.net  It gives lots of info about a solved pic  which may be of use in setting the right info into asiair.

 

@MalcolmP  Last night it found more 900 + which I thought hurrah but the FOV was over the max threshold.  At that stage of the evening I was still at a loss to how to fix it.  I'm hoping to with a higher focal length I'll get there.

Thanks for the tip on the website, I'll be sure to give that a go.

Edited Friday at 12:19 by Blaired79

[Elp]

Did you get the same issue with the 55mm? You can also take a short preview image in preview mode at the same duration exposure being used when plate solving and post the images here for us to look at.

[Blaired79]

@Elp I can’t recall.  I was also fighting against a misted lens too but I have a lens heater to hopefully solve this. The next cloud free night for me is Sunday, I’ll try a few lengths and share the previews here. Thank you!

Edited 10 hours ago by Blaired79