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Delphinus nova and some widefield shots

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#1 Dave Kodama

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Posted 17 August 2013 - 01:47 AM

In case you haven't heard, a nova was discovered in Delphinus a few days ago. It has apparently reached naked-eye visibility, so it is an unusually bright one.

By chance, I had photographed the area during the Perseid meteor shower and also one week earlier, so I went out on Thursday night to shoot a few more shots so I could get some before/after photos:

http://astrocamera.n.../DelphinusNova/

These are a few more widefield shots I was taking during the Perseid shower:

http://astrocamera.n...0811/widefield/

I used a 4-point star filter to bring out the colors of the brighter stars.

Dave

#2 Nebhunter

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Posted 18 August 2013 - 01:50 PM

Nice capture Dave. Nice to have a nova or two on the resume. BTW - do you use any focus aid for the 165 lens - or just the lens stop for infinity?

I've done a bit of testing with the Stiletto and 300 lpi Ronchi screen. I've found that Pentax lenses that go past infinity. My SMC165 reaches perfect focus with the diamond exactly at the beginning edge of the infinity symbol.

The SMC200 lens - place the | line under the hyperfocal 8 exactly in the centre of the infinity symbol. The Takumar 300 lens is the same with | 8 on the left side centre of infinity - and right side | 8 would be directly under the 1 of the 100. I think the Tak 300 is further out as the rear of the lens has the square threaded area to hold gel filters which would really change focus.

My 400 edif goes well past infinity, but has a lock to hold it in position once found. How much difference does it makes? It is a fair amount of movement from perfect focus to lens stop. The Ronchi lines appear in quantity - 3 to 4 lines depending upon the lens at the lens stop. Back off focus to the spots I've mentioned and they are gone. Conditions were good and I used Vega. Ronchi lines were very steady and not wavey which would indicate poor conditions. Test was repeated about 10 times on two consecutive nights. Same results. End result to my mind would be sharp stars vs pin point stars.

igor

#3 Michal1

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Posted 20 August 2013 - 05:56 PM

An interesting series. Congratulations Dave.

#4 Dave Kodama

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Posted 21 August 2013 - 08:55 AM

Igor,

The Pentax lenses I use all focus fine right at the infinity stop for E200 because the fast ones seem to be well calibrated or I stop lenses down for image quality reasons. For example, I shot the 165 at f/4 instead of f/2.8 to maintain decent stars out to the edge. Also if I used a film with a thinner base, it's possible I would have to offset focus as my vacuum backs pull the film back to the vacuum plate surface.

I seem to have more serious focus problems due to scanning because of film curl as my scanner's film holder only holds the film on 3 edges unless it's a full 6x9 frame.

Dave

#5 Nebhunter

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Posted 29 August 2013 - 12:42 PM

Dave - I've found the 165 lens to be about where the infinity stop is past infinity. You know what I mean. I do not have the Stiletto calibrated for a vacuum back - just standard film.

I also have a vacuum back but have not had a change to shoot the 165 with it. Actually I have not had one night this year due to weather and other conflagrations.

If I get a chance I will do so for comparison. I wonder how much change their is with vacuum back, as the pressure plate is adjusted to 220 setting??? Certainly having a nice flat film makes a difference. Might be worth a quick shot of a star cluster at my suggested settings and see what you get.

igor

#6 Michal1

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Posted 29 August 2013 - 03:03 PM

My "new" 200mm SMC has the infinity focus here. I learned it by performig a variation of the star trail focus test.
Igor, is it necessary to calibrate you focuser somehow?

#7 Nebhunter

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Posted 01 September 2013 - 08:53 PM

Yes Michal that would be the best way. Send the camera in to have the Stiletto matched exactly to the camera. Right now mine is done to the specifications in the manual and lets face it, things change after 30 years.

That may be the case with my unit as I'm quite a bit further that your setting - which seems to make more sense than mine.

igor






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