Why might my setup be producing blurry images?

[pipnina]

Hi!

I set up my HEQ5 synscan and it seems to be maintaining tracking quite well, since I have had my camera shooting for hours now and orion is still in the same spot (save me going out to nudge it on RA/DEC via the handset to pseudo-dither), but every picture shows stars that look considerably bloated or even stretched out!

I will attach images here shortly (once I've retrieved the SD card when the battery in the camera dies in the next hour or so) which might help you guys help me work out what's wrong.

I tried my best to make sure RA/DEC are balanced, double checked the clutches are tight, the air in my garden is quite still. I did the two-star alignment and it's only set to sidereal rate and not sidereal+PEC. I seem to have rather random luck as to whether the mount will produce sharp images with good tracking or perform horrendously like this! It's on grass but I always give it a good wiggle and press into the dirt before I start polar and 2-star alignment.

I have even checked for dewing (and de-spidered it, that guy worked fast!) and re-focused it a few times. It looks quite sharp in the camera live screen but any 2 minute shot I take comes out looking just as bad! Any tips for making my setup more consistently performant? Any ideas what might be causing this issue with the mount because everything I can think of that I can control comes up fine : (

Any ideas appreciated!

[Budgie1]

How are you doing the Polar Alignment and is the mount level?

On my own HEQ5 the built-in spirit level has been put in on the skew, so I've fitted my own and use that.  

[pipnina]

1 hour ago, Budgie1 said:

How are you doing the Polar Alignment and is the mount level?

On my own HEQ5 the built-in spirit level has been put in on the skew, so I've fitted my own and use that.  

I do polar alignment in a lightly naughty way: I let the mount tell me what hour angle it's meant to be, and roughly get it to that hour angle in the guide inside the mount's optic, but it is on the edge of that circle and pretty close I'd guess, even though they designed a system where that optic is pretty much impossible to get to the right position...

As for if the mount is level... Hmm. I hadn't considered such matters! I didn't even check the sight glass on the mount. I will have to see what it looks like in the morning, since I just took the camera off and came indoors leaving the mount in the garden.

Here are some close-ups from the camera, about an hour apart and in center frame,

[david_taurus83]

Are you not guiding?

[pipnina]

5 hours ago, david_taurus83 said:

Are you not guiding?

Sadly not at the moment, which of course would be great to add to my setup but I hear even without guiding my HEQ5 should manage some shorter times (like these 2 min shots) without effects as severe as those shown?

[Skipper Billy]

I think you have answered your own question!

Not really accurately polar aligned, set up on soft earth and not guiding.

I didn't see which scope you are using for these images but if its the SW 250 I am surprised the images are as good as they are - its a big ask for a HEQ5!!

 

[david_taurus83]

2 hours ago, pipnina said:

Sadly not at the moment, which of course would be great to add to my setup but I hear even without guiding my HEQ5 should manage some shorter times (like these 2 min shots) without effects as severe as those shown?

Im not sure of the exact specs for the HEQ5 but I can tell you a conservative figure for my AZEQ6 periodic error is say 30 arc seconds peak to peak over the 7 minute worm cycle. Thats a shift of over 4 arc seconds per minute and would be 8.5 seconds over one of your 2 minute subs. If you are using a 250P then I reckon you are shooting at less than 1 second per pixel so on my mount that would be an 8 pixel movement over the 2 minutes. Perfect polar alignment wont fix this I'm afraid. As David points out above, it is probably a combination of all things considered. If you are shooting with a focal length of 300/500mm then you will have a better chance.

[City9Town0]

From my HEQ5....

[pipnina]

35 minutes ago, david_taurus83 said:

Im not sure of the exact specs for the HEQ5 but I can tell you a conservative figure for my AZEQ6 periodic error is say 30 arc seconds peak to peak over the 7 minute worm cycle. Thats a shift of over 4 arc seconds per minute and would be 8.5 seconds over one of your 2 minute subs. If you are using a 250P then I reckon you are shooting at less than 1 second per pixel so on my mount that would be an 8 pixel movement over the 2 minutes. Perfect polar alignment wont fix this I'm afraid. As David points out above, it is probably a combination of all things considered. If you are shooting with a focal length of 300/500mm then you will have a better chance.

 

20 minutes ago, City9Town0 said:

From my HEQ5....

-snip-

I see, expecting too much of my kit as usual I suppose!

I am using the 130-PDS so I have a 650mm fl. At around 1.22 arcsec/pixel, so that could still be 5pixels or so drift by your measurements assuming good polar alignment too...

I can feel my bank account shrinking already, time to google for permanent mounting solutions and guiding equipment haha.

Thanks for the pointers guys!

[City9Town0]

Guiding (and expense) is the way forward!

[david_taurus83]

Guiding will transform the mount. It will correct for periodic error and slight polar misalignment. It doesn't need to be too expensive. A small 30mm guide scope will be fine and a camera. £150 all in if you look for used kit.

[Varavall]

18 hours ago, pipnina said:

Hi!

I set up my HEQ5 synscan and it seems to be maintaining tracking quite well, since I have had my camera shooting for hours now and orion is still in the same spot (save me going out to nudge it on RA/DEC via the handset to pseudo-dither), but every picture shows stars that look considerably bloated or even stretched out!

I will attach images here shortly (once I've retrieved the SD card when the battery in the camera dies in the next hour or so) which might help you guys help me work out what's wrong.

I tried my best to make sure RA/DEC are balanced, double checked the clutches are tight, the air in my garden is quite still. I did the two-star alignment and it's only set to sidereal rate and not sidereal+PEC. I seem to have rather random luck as to whether the mount will produce sharp images with good tracking or perform horrendously like this! It's on grass but I always give it a good wiggle and press into the dirt before I start polar and 2-star alignment.

I have even checked for dewing (and de-spidered it, that guy worked fast!) and re-focused it a few times. It looks quite sharp in the camera live screen but any 2 minute shot I take comes out looking just as bad! Any tips for making my setup more consistently performant? Any ideas what might be causing this issue with the mount because everything I can think of that I can control comes up fine : (

Any ideas appreciated!

I started out with the HEQ5 Pro, SW 200pds and a Nikon D5200 and generally I could really only manage 60 second subs without problems. Some days could make it to 5 minutes but they were few and far between. Yes, now I guide, done a Rowan belt upgrade and have a half decent cooled camera. But before you shell out the money for guiding, you could do a few things in the meantime. Adjust the backlash out of the worm gears; ensure a good balance of the rig (the tube is rotated so the camera is on the mount side?); get a good polar alignment (the polar scope does a reasonable job if used with a polar scope app); and if possible set up the scope permanently ( I made a pillar mount out of scrap aluminium and cover up with a clamshell motorbike cover). Taking down and setting up the rig is a pain and is a cause of continuous errors; if permanently setup, each error can be addressed leading to less stress and more observing time. I hope I have given you some food for thought.