alacant

8 hours ago, Nigel G said:

tightening in the magic

StarTools Magic. It's magic:)

9 hours ago, wimvb said:

also don't understand the diagram

Hi. I think one only obtains a regular ellipse -the shape of the secondary- by taking a section through a cylinder. A conic section -the light from the primary- has the minor axis displaced toward the 'fat' end of the cone. I can only explain it by doing it:

3 hours ago, Stub Mandrel said:

line up on the centre of the secondary

Hi. At f5, the secondary should not be centred. Centre, yes. Then displace. It looks something like this. HTH.

9 hours ago, dyfiastro said:

Any suggestions and advise would be great

Hi. Do your flats clear the problem? Unless the issue is affecting your photos and the flats are doing their job, I'd forget it. I think the procedure is to centre the secondary then displace it 3mm both toward the primary and away from the focuser. But life is short... HTH.

On 10/11/2016 at 04:39, Stridor said:

Tips or advice very welcome.

Hi. Even on modified cameras where the camera ir filter retained, it's never strong enough and the ir records as unfocused visible, especially with refractors, no matter how APO they maybe. One of these will tighten the stars back to normal. No need to go brand name. They all come from the same factory in China. AliExpress or eBay sources are fine. Around €15. Add a wratten#8 -marketed as fringe killer at 10 times the price- and you really are in business. HTH.

Hi. Here's my first snap with a camera attached to a telescope. 1999. FujiColor film. You peered through the illuminated eyepiece and guided by keeping a star on the cross-hairs using the hand controller. I resurrected the telescopes last year. How things have changed. Nostalgia.

15 minutes ago, SteveNickolls said:

wide shot of part of Auriga

The clusters look amazing in your composition. Hope you don't mind, I'm learning colour balance ATM. I took the curves down a bit. Probably way off now! Clear skies.

16 minutes ago, Stub Mandrel said:

Finally fixed my extra diffraction spike issue! I have confirmed the cause as focuser tube ingress into the light path.

Ah. OK. Is this with the sw cc? I was getting D shaped stars to one side of the frame when the camera was aligned with the focuser knobs. On my reflector, it takes the focus tube 1cm further into the main tube and so interferes with the light path. Moving the mirror caused vignetting so I cut the end off the focuser. Am I correct in believing that the gso cc allows focus at the normal position and so negates the ingress? TIA.

2 hours ago, parallaxerr said:

through ST to see what's there.

That's a really nice image crying out for the rather nice ST Life module. Worth a try?

19 minutes ago, Stub Mandrel said:

a filter on eBay for £10

Hi. I've a sneaky feeling that some outlets buy them in bulk, write Baader or Optolong on them and knock 'em out for 10 times more;) 

7 hours ago, Filroden said:

second image almost looks like a narrowband in the Hubble palette!

...but far less jump-on-the-bandwagon-oh-so-predictably boring!

34 minutes ago, SteveNickolls said:

Synscan does the nudging pretty well all by itself

Unfortunately it always nudges in the same direction. Hence the importance of randomly. AKA dither. HTH.

2 minutes ago, The Admiral said:

not using darks may not be sufficient

Light, flat and bias frames and randomly nudge the mount a little after each exposure maybe too? HTH

1 hour ago, The Admiral said:

I get the feeling that one needs to replace them with something else

Flat and bias frames? HTH

13 hours ago, parallaxerr said:

Exposure time vs CA?

Hi. I've an affordable refractor too and have managed to tame the CA [1]. The cure is a uv-ir cut filter -to help the inadequate in camera filter and prevent those wavelenhgths recording as visible- with deconvolution of the blue channel so as to push the blue back to the central star. The method is unfolding here... HTH.

[1] Which IMHO is infinitely better than having hideous spikes protruding from every star!

Hi everyone. Short tube, big secondary and proper 2 1/2" r&p focuser; the new Bresser 150/750. Makes pds' look decidedly dated! Just add CC for instant AP.

1 hour ago, Nigel G said:

Can I do that with data from a dslr? 

Absolutely. The LRGB module will pull only the channel(s) you choose, be it separate files or a colour stack. HTH.

1 hour ago, Nigel G said:

reduced the stars by a huge amount already

Hi. StarTools right? It looks like the blue has fattened the stars: Load the blue only in LRGB, Autodev. Decon, radius 3.0*, 1 iteration, show result. Restore to Linear Wiped Deconvolved. Save that as blue.tif. Now fire up LRGB again, load the Red and Green from the original but use your blue.tif for the blue. It concentrates whichever channel is 'fat' back to the central star. After killing tracking, Magic a pixel or two. HTH.

*That's my starting point. YMMV

On 3/11/2016 at 09:50, Stub Mandrel said:

instead of telling beginners not to bother trying imaging unless they have masses of expensive kit, they can see the possibilities of imaging on light and alt-az mounts

+1. Again and again: have a go with what you have. There's not enough experimentation. Things really have moved on from the EDsomething on an eq6 days. And IMHO for the better.

Hi everyone. I was fed up of galaxies being a small spec in the frame so I set up this old 6" refractor to have a go at Stephan's Quintet. Still quite small but at least identificable as galaxies this time. Despite many dismissing it out of hand, I think it worked quite well on my dslr. Having said that, when it was first made -in the mid 90s I think- I doubt whether this would have been possible without a house remortgage! Cheers and clear skies. 

2 hours ago, The Admiral said:

Not quite sure why that should be so

Hi. No expert but I believe it is because of the canon sensor recording invisible radiation as blue at one end of the spectrum and red at the other; it shouldn't. It's the same effect that makes the stars fat. A #8 reduces the blue and a #12 eliminates it, but I don't think that's what you're aiming for (?).  HTH.

2 hours ago, parallaxerr said:

disappointed with the CA still

The semi-apo doesn't really do CA; I think it removes around 50%. A uv-ir plus a skyglow I find works better but still a great shot. HTH.

6 hours ago, parallaxerr said:

The CA is there

Hi. We've a thread on the StarTools forum. Basically we decon the blue channel back onto the central star then pull the RG separately on top of the de-convoluted blue. It sounds complicated but do it a few times and it becomes second nature. Helping the weak Canon uv-ir filter -it records them as visible- at source with a proper uv-ir block filter really helps too. If you just want a quick fix, put the fat stars in a mask and the hit filter > fringe killer. The problem with the latter is that the halos are still there, just in a shade of grey. But hey, it sure beats having spikes sticking out from every star!  HTH.

1 minute ago, parallaxerr said:

orange/brown to start with

...just the moon and skyglow then. No need to spend a fortune!

Here's a side by side. Both have moon and skyglow which removes the muddy orange. The better image is with the uv-ir I mentioned. Under €25 for both on AliExpress. HTH.

**Taken on an eq so not strictly on topic but I thought my experiment findings -all by coincidence of choosing the wrong filter in the dark- may help other achro ap users. If you want to eliminate the ca completely you can use a 495nm long pass (wratten 12) along with the uv-ir -useful for e.g. the horsehead where there is a bright star in the fov.