Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

Welcome to Stargazers Lounge

Register now to gain access to all of our features. Once registered and logged in, you will be able to contribute to this site by submitting your own content or replying to existing content. You'll be able to customise your profile, receive reputation points as a reward for submitting content, while also communicating with other members via your own private inbox, plus much more! This message will be removed once you have signed in.

  • Announcements

    sgl_imaging_challenge_banner_nlc.gif

Sign in to follow this  
Followers 0
Stub Mandrel

Vertical bit of the learning curve!

11 posts in this topic

Well I have the western veil in my sites, probably  a bit off target, but I don't care, there's a streak of red on the preview screen and that's enough to make me happy!

Why? I've gone from 0-60 in one night and it's an exciting ride. The cooler seems to be cooling (after a heart-stopping connector fail which made me think I'd connected the leisure battery back to front...)

I was expecting guiding to be a nightmare. PHD2 was just giving me a grainy screen and I couldn't find any stars, let alone focus. I switched to Sharpcap and used FWHM to easily get a half-decent focus.

Back to PHD2, connect, centre and select a star, click guide and turn on a few windows so I can see that famous graph.

What's it doing? Gradually realise it's testing out the mount. Faint changes in the sound of the steppers. Good grief, perhaps my box is wired up and programmed right!

At last it announces it's guiding!. Some big excursions, especially in dec. Not surprised, lots of backlash. Discover that looking at previews on the camera upsets the guiding -DOH. Still, histogram right at left on 1 minute (ha filter) I'll try five...

Back to the graph. Change x-axis to 16, that looks better - yes I know it's only cosmetic LOL!

What 'star lost mass change' ... w'happen? Run for google... it's the changing conditions, I must find the 'brain' then turn off star mas detection as its a clear star on its own.

Graph settling down a bit, still DEC worse than RA. The big RA shifts seem to happen after I walk past the scope - I've noticed this before when videoing planets, the grass shifts under my feet.

So... best thing is to leave it all alone for an hour or more and see what happens.

Then I can read the long term stats, try and understand them and see what needs to be improved.

1 person likes this

Share this post


Link to post
Share on other sites

Wow, I'm a happy bunny!

It's an hour since I left the scope alone, the stats say my RA RMS error is 0.17 and DEC RMS error is 0.13.

The PHD2 documentation says "Just as a rough starting point, you probably want to see your
total RMS value be 1 a-s or lower. How much lower will depend on many things, especially your
seeing conditions and the quality of your mount." 

I'm going to assume those results are pretty impressive for an EQ3 mount.

:glasses9:

Share this post


Link to post
Share on other sites

Welcome to the stressful world of Astro Imaging. 0.13 is impressive for the EQ3 and will show in your images as nice round stars. Don't forget to post your images.

Steve

1 person likes this

Share this post


Link to post
Share on other sites

Looks like beginners luck, although it settled down nicely on the veil, I went up to the pelican and the Dec went crazy with the scope pointing almost upwards, RA was less than 0.2, but dec went up to 1.5 RMS with much bigger saw-tooth swings - it's all the backlash when one end isn't weighted.

I will put up the results but it seems all photos out of focus and worse on one side... (1) next time switch on cooler before focusing and (2) looks like the shim that stuck to the  sensor when I removed it should have been put back on the right side, not the left...

At least I got to prove the guiding can work and play with lots of settings.

Also discovered that I need to turn off guiding at the computer before turning it off at the mount - otherwise PHD starts rampaging randomly through the menus which are handset controlled!

Share this post


Link to post
Share on other sites

Hi Neil,

There is a lot to learn with astro imaging, especially if you are setting up & tearing down each session. The best advice I can give is to practise during the day, cloudy nights etc.. Setting up and getting everything ready until you can do it with ease. Also, a good old pen & notebook to write down any settings or changes you may make. With our fickle skies it could be weeks between imaging sessions and if your brain is as good poor as mine you will have forgot everything :icon_biggrin:

 

Steve

1 person likes this

Share this post


Link to post
Share on other sites
3 hours ago, sloz1664 said:

Hi Neil,

There is a lot to learn with astro imaging, especially if you are setting up & tearing down each session. The best advice I can give is to practise during the day, cloudy nights etc.. Setting up and getting everything ready until you can do it with ease. Also, a good old pen & notebook to write down any settings or changes you may make. With our fickle skies it could be weeks between imaging sessions and if your brain is as good poor as mine you will have forgot everything :icon_biggrin:

 

Steve

I'm not too stressed about setup/teardown - I set aside an hour well ahead of sundown, plenty of time to check everything before dark at this time of year. I'm sanguine about 'spending' some darks nights on getting consistent results.

One thing I can do is address the 'stiction' in DEC, when pointed up my DEC trace was pretty much identical to this one from one of the PHD2 tutorial PDFS, except it did have some extended 'flat' stretches between.

 

Share this post


Link to post
Share on other sites

Posted (edited)

<edit> removed nonsense caused by looking at wrong subs!

This is a screen-grab close-up of a totally-unprocessed 300s RAW taken at random from the first run when the RMS figures were really low.

Looking across the image, I think the shim went in the right place, which means that I need to increase the demisting current as the doughnuts are probably condensation...

temp.thumb.jpg.d02d62036fc7a3410fab1f2e62f3d797.jpg

Edited by Stub Mandrel

Share this post


Link to post
Share on other sites

Well possibly the worst Ha image ever...

In focus across the frame?  - TICK!

Captured Plenty of Photons? - TICK!

Round stars? - TICK (I think)!

Thick coating of ice/condensation on front of sensor? - TICK!!!!!!

Veil.thumb.jpg.7eea7b054fd2e1ccfbb25e2ee1fc9276.jpg

Share this post


Link to post
Share on other sites

Here's a RAW of the pelican converted to jpg...

The doughnuts suggest blobs of something on the filter glass. A bit bigger than dust doughnuts and bright rather than dark, suggesting  condensation or ice.

Good news is the stars that show through are focused across the frame.

The DEC issue is definitely there on many, but not all, of the 'straight up subs' the stars are stretched vertically but not on the subs at a less severe angle.

Well this IS a learning experience :-)

Pelicrap.thumb.jpg.43515aba78f2dcc89099d41b9c0cdbd4.jpg

 

1 person likes this

Share this post


Link to post
Share on other sites

Hope you get the cooling system working properly soon Neil, I want to try autoguiding myself eventually on the EQ3 so I'm interested to see your progress

All the best, Art

Share this post


Link to post
Share on other sites

I've reduced the dropper resistor to 50R from 220R but the way the maths works this will be a lot more than four times as much warmth, about a quarter of a watt, which is what some other folks use.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0

  • Recently Browsing   0 members

    No registered users viewing this page.