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Gina

Thoughts on which imaging rigs to concentrate on

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I've added the Delrin spacers and measured the spacing again.  49.92+6.5 = 56.42mm.  Hmmm, a discrepancy of several tenths of a mm - I don't think my measurement is all that accurate or maybe the rings compressed when I measured them with the digital calipers or there might have been dust on the surfaces or ...

59add25ad68ac_BackFocusMeasurement02.thumb.JPG.1b0f21d89290414e801845f196636eef.JPG

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With the new camera and just the 0.15mm spacer I get about 49.5mm (0.03mm tolerance) making a total of 56.0mm as near as I can measure so that's it :)

 

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A lovely orange full moon rose in the east a little while ago :)  If you like that sort of thing :D  "Harvest Moon" I believe :) It's lighting up the passing clouds beautifully :happy6::clouds1:

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  1. The single widefield imaging system is nearly ready - just needs a pinion printed for the remote focus. 
  2. Dual widefield NB imaging rig requires support structures and remote focussing systems for both lenses and electronics.
  3. Esprit Imaging rig just needs assembly - all parts ready to go and now includes OAG for guiding.
  4. Ha solar telescope imager needs a couple more printed parts and electronics box.

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The weather forecast is dire for any nighttime imaging but there is some chance of daytime with Ha solar so I think I shall probably be working on the Ha solar setup.  Alternatively, I may feel like a complete change from anything astro and might work on my perpetual calendar.  Not doing anything on my projects this evening so I'll just see what I feel like tomorrow  :D

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Actually, I have diverged from all my usual projects and set up a vinyl music system and really enjoying playing some of my old records that haven't seen the light of day for decades :D  Beats watching much repeated oldies on the telly :D

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I have just won an auction on ebay for a 28mm f2.8 Pentax M lens which I can put with my present 28mm f3.5 lens for dual imaging :)  Cost just under £42 including postage.  Once I receive this lens and sort out an adapter for its Pentax K mount I shall have doubles of all my lenses and my main push will want to be on the dual imaging rig.

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Amazingly a clear night and I made what I consider a valiant attempt to get imaging with my single widefield rig.  Unfortunately, things didn't go according to plan (now there's a surprise!!!) and severe problems with focussing which I find very puzzling as I feel sure I had this rig working some time ago. 

Anyway, with apparently no chance of any more imaging for a week or more I shall move on to the dual widefield imaging rig - the second 28mm lens should arrive in the next day or so.  I have learnt that I could do with finer focussing for the KStars/Ekos/INDI auto-focussing system to work properly so at least last night wasn't a complete loss :D

Edited by Gina

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Having looked at images of The Milky Way in the Widefield forum, I'm thinking I would like to image with a wider FOV than the 28mm lens but not as wide as my all sky camera.  The ASC covers the whole of the MW but with lower lower resolution than I would like - probably less than 2000 pixels for the whole length.  Also the ASC is luminance only.  It would be nice to capture it in higher resolution and colour.  Hmm... I could try a DSLR :D  No, no, no, mustn't take on yet another project - I already have too many on the go!!! :D

What I really had in mind was to use an old SLR lens of shorter focal length than 28mm but this takes me into the fish-eye range and rocketing prices eg. Pentax Fish-Eye-Takumar 17mm F4 Manual Focus Lens Pentax Screw / M42

Edited by Gina

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Another idea, I could try the zoom lens off my Canon 1100D - minimum FL of 18mm at f3.5.  I have a Canon EOS mount to T2 adapter (somewhere).

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I've picked up another cold from somewhere and feeling far from inclined to do much so I won't be :(  Worst of it is a sore throat together with cough and muzzy head.  I shall just have to take it easy - as long as I sit quietly I don't feel too bad.  Until I feel a bit better all projects are on hold :(

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Wishing you a speedy recovery Gina and whilst resting no more thoughts on future projects :icon_biggrin:

Steve

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I'm just relaxing, playing some very old records that I haven't played for decades :)  As a scientist and engineer I can't explain why analogue reproduction sounds smoother than digital but it does :)  I can only think that the human ear/brain combination is more finely tuned than can be explained by science.   I've also ordered a couple of vinyl records in the hope that these will be free from clicks and pops that my old records have and that no digital processing has been used in their production.

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On 24/09/2017 at 16:15, Gina said:

I'm just relaxing, playing some very old records that I haven't played for decades :)  As a scientist and engineer I can't explain why analogue reproduction sounds smoother than digital but it does :)  I can only think that the human ear/brain combination is more finely tuned than can be explained by science.   I've also ordered a couple of vinyl records in the hope that these will be free from clicks and pops that my old records have and that no digital processing has been used in their production.

Hi Gina

Long time after the last post, hope you are keeping well. I saw a post from you about lens to use with the ASI1600 and can't find it. I will get back to you shortly. Regards

Alec

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Gina

Here I am again. On another stream I have been posting about problems of star trailing etc still to be resolved with my Skywatcher ADventurer and ASI1600MC camera and TSAPO60 scope. So last night I lightened the rig and simply had  a Canon 55mm lens on the end of the ASI1600. A quick stack and stretch (attached) showed a woeful image of stars. It has to be said that seeing was pretty bad with high misty clouds passing through.

As and expert I would value your input to the issues on the image and what lens (not too expensive) would give me a reasonably flat image? Ultimately I want to take a wide field image of the Milky Way. Should the 55mm lens be better than this.

Many thanks for your input

Best wishes

Alec

 

 

163040174_quickstack55mmlensASI1600MCcamera30ssubs.thumb.png.ba973b00011ef61bd4bb8b50d6b65192.png

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Canon 55mm lens? Is that the 18-55 standard zoom that comes with canon dslrs? IMO this is not a wonderful lens. For a canon you can do a lot worse than pick up a "nifty fifty" - 50mm f1.8 II - but make sure that you get the Mk II version. I have used this with my 1600 and got some reasonable results.

That said, the way the stars are stretched is almost as if there is insufficient distance to the chip (see attached pic). Presumably you are using the zwo adapter? As you have the filterwheel, I wonder if you are using the "short" adapter (that allows for filterwheel to be added)? If so, you would need an extension to make up the distance if using it without the filterwheel.

too close.jpg

Edited by Demonperformer

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10 hours ago, Demonperformer said:

Canon 55mm lens? Is that the 18-55 standard zoom that comes with canon dslrs? IMO this is not a wonderful lens. For a canon you can do a lot worse than pick up a "nifty fifty" - 50mm f1.8 II - but make sure that you get the Mk II version. I have used this with my 1600 and got some reasonable results.

That said, the way the stars are stretched is almost as if there is insufficient distance to the chip (see attached pic). Presumably you are using the zwo adapter? As you have the filterwheel, I wonder if you are using the "short" adapter (that allows for filterwheel to be added)? If so, you would need an extension to make up the distance if using it without the filterwheel.

too close.jpg

Thanks for getting back. Apologies, in my haste I posted duff info. I should have said the image was taken with the Canon EF 50mm 1:1.8 II  lens. the very one you mention. I have this on the end of the ASI1600 MC camera, no filter wheel and is connected with the ZWO EOS T2 adapter without the additional 5mm T2 extender. My set up is shown attached.

ASI1600 spacer attachments.JPG

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28 minutes ago, alcol620 said:

Thanks for getting back. Apologies, in my haste I posted duff info. I should have said the image was taken with the Canon EF 50mm 1:1.8 II  lens. the very one you mention. I have this on the end of the ASI1600 MC camera, no filter wheel and is connected with the ZWO EOS T2 adapter without the additional 5mm T2 extender. My set up is shown attached.

ASI1600 spacer attachments.JPG

Should this all works or is the spacing wrong?

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Checking at the info on the FLO website, it looks as if you are using the correct spacing (no extender for the 1600) - as such I really don't know what is causing the star pattern. Someone else may be able to shed some light on it. In the meantime the first thing I would do is check if you get the same effect when you take astro pics with this lens on your 550D. If you do, it might be a problem with that particular lens. If you don't then the lens is ok and the problem must lie elsewhere.

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Using a lens wide open show all lens aberrations to their max. Did you stop the lens down at all?

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Just now, happy-kat said:

Using a lens wide open show all lens aberrations to their max. Did you stop the lens down at all?

What do you stop it down to?

DP do you have yours stopped down?

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5 minutes ago, alcol620 said:

DP do you have yours stopped down?

I run mine at f2.8 or f4.

When you stop down the lens you are only using the central part of the glass. The curvature on the elements is strongest at the edges and is hardest to get "perfect" and tend to be the worst part of the lens (that's a relative term with a manufacturer like Canon). Stop it down and you are only using the "best" bits of the elements within the lens and so overall get a better result.

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14 minutes ago, Demonperformer said:

I run mine at f2.8 or f4.

When you stop down the lens you are only using the central part of the glass. The curvature on the elements is strongest at the edges and is hardest to get "perfect" and tend to be the worst part of the lens (that's a relative term with a manufacturer like Canon). Stop it down and you are only using the "best" bits of the elements within the lens and so overall get a better result.

Why do you use 2 different settings? Photography and cameras are not my top subject! Thanks

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