Jump to content

 

1825338873_SNRPN2021banner.jpg.68bf12c7791f26559c66cf7bce79fe3d.jpg

 

M92 17.06.11 TS 8" f/4 first light


Revs
 Share

Recommended Posts

Hi guys. Just finished processing my first DSO, M92 :)

Lots of firsts tonight. First night out with the newt and first guided image. Overall I'd say it's gone well. After 2 weeks waiting for a good night I decided tonight was the night. The seeing was good but transparency was poor, plus the Moon was out making the sky glow slightly.

I think the MPCC spacing or the collimation needs tweaking, as you'll see on the larger pic in the link. Maybe a more experienced imager could advise :) The image was processed in DSS and tweaked in Lightroom.

Any feedback appreciated, cheers for looking B)

Details:

TS 8" f/4 Newt (MPCC)

HEQ5 Pro

QHY5 through 9x50 finder

Mod'd 1000D with 2" CCD CLS

40x 40sec lights

10x 40sec darks

1x bias

0x flats

post-20885-133877619553_thumb.jpg

LARGE

Link to comment
Share on other sites

Cheers guys :). I'm gonna have another go at processing it this aft as the stars seem to have lost their colour in DSS. I'll try re-doing it with different settings. I'd not used DSS before so I suspect I've got something a bit wrong somewhere. I think I went slightly too far of the sharpening, too.

As for the star trails, they look to be all going the same way to me. Would that be tracking? All the subs are the same in this respect.

Thanks again.

Link to comment
Share on other sites

Paul, nice start :)

Bung up a single sub to show off the star shapes better, not sure that DSS hasnt stacked two pics without matching the stars properly. Getting the spacing to mpcc right can be tricky to say the least!

If you must use the 16bit file that DSS spits out, you may like to tweak the saturation a little.

Tim

Link to comment
Share on other sites

Hi tim, cheers :)

If you must use the 16bit file that DSS spits out, you may like to tweak the saturation a little.

What's the alternative? I'm totally new to DSS.

Here's a light, untouched other than being converted to jpeg. All the lights are pretty much identical..

http://img607.imageshack.us/img607/826/m92170611.jpg

Edited by Revs
Link to comment
Share on other sites

Cheers guys :). I'm gonna have another go at processing it this aft as the stars seem to have lost their colour in DSS. I'll try re-doing it with different settings. I'd not used DSS before so I suspect I've got something a bit wrong somewhere. I think I went slightly too far of the sharpening, too.

As for the star trails, they look to be all going the same way to me. Would that be tracking? All the subs are the same in this respect.

Thanks again.

A nice start Paul. The trailing does look like a tracking issue as it is all in the same direction.

Regards

Kevin

Link to comment
Share on other sites

Firstly, a good start.

To my eye there is more distortion on the left hand side than the right and it is not entirely in the same direction, though it nearly is. The elongation is slightly radial across that side. So I don't thnk it is tracking.

I don't know what collimation effects arise when imaging with Newts so can't comment. However, I would be suspicious of the orthogonality of the chip relative to the light cone. Deflection in the tube? Droop in the focuser? Camera simply not in the focuser perfectly? All very important at fast f ratios.

Olly

Edited by ollypenrice
Link to comment
Share on other sites

Cheers Olly. I'll give the newt another full looking over. The collimation of all the various bits, focuser, secondary and primary, takes some doing. I'm still very much in the learning stage, so I'm sure it'll be me that's got it a bit out. Maybe the secondary is rotated out of alignment.

Thanks again for your comments and tips, peeps :)

EDIT: The stars in the lower right look a little triangular. I'm wondering if I over-tightened the primary cell's locking screw, distorting the primary.

Edited by Revs
Link to comment
Share on other sites

Ive often wondered how these newts perform, it would be nice to see it turned on a nebula. F4 is a distant dream for me at the moment!

For a moment I thought you still had a bit of coma, but the opposite corners arent consistent in the amount of mis-shapen stars so youre probably right in thinking its collimation or mpcc spacing. So youre in for a bit of tinkering before its settled :)

Link to comment
Share on other sites

It does look like the collimation is a bit out with respect to the camera.

As a simple test in rainy weather, attach the camera to the scope as normal, point the tube at a white wall or lightbox and shoot a few flats. Put them on the 'puter and stretch them a bit. Is the vignetting nice and concentric with the centre of the image?

If you are using a laser collimator, you might want to look into the barlowed laser technique - might help on these ultrafast newts.

Newtonian collimation with lasers and using barlows in the Barlowed Laser Technique

Scroll down to part three

You could even look down the viewfinder as a simple test?

It suprises me that manufacturers don't supply these fast news with a laser collimator that fitted out for this type of collimation, and designed to M42 thread onto the focuser, instead of the 1.25inch eyepiece barrels that most laser collimators are built into

Edited by Tom How
Link to comment
Share on other sites

Cheers for the comments, guys :).

Tom, I like the sound of the vignetting test method, as it's something I can do during the day. As for collimation, yup I'm using a laser collimator, which itself is deffo collimated. And I do use the barlowed method for the primary.

I checked and double checked the collimation after mounting the scope on the HEQ5. I'm confident it was as good as can be, but as Dion points out in his YT vids, a laser collimator won't tell you if the secondary is rotated out of alignment, as it can still collimated and look correct. I'm 90% sure it a combination of this and the MPCC spacing. If I get chance I'll do some hardcore collimation testing over the weekend.

Thanks again :)

Edited by Revs
Link to comment
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
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.