Re: [APML] New TP pictures

[Duncan <dmunro@sfu.ca>]

I think this effect is caused by a plume of air moving between the 
corrector plate and the primary mirror, so your dewheater was in the 
"optical path" even if you couldn't see it... ;-) 

I 've taken  long exposure shots with an older 10" OTA as well, but I 
used a heated dew cap so the tube itself was unaffected by tube 
currents, and I didn't get any spike effects.

cheers

Duncan

joe wrote:

> Yes, but it was never in the optical path...joe  :)
>
>
> "May You Go Among The Imperishable Stars"
>
> Joe Mize:     jmize@svic.net
> StarFields Observatory   http://www.cav-sfo.com
> Chiefland, FL    29:24'33.4"N    82:51'37.7"W
> Moon Phase:     http://tycho.usno.navy.mil/cgi-bin/phase.gif
>
> ----- Original Message ----- From: "Duncan" <dmunro@sfu.ca>
> To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> Sent: Friday, March 18, 2005 12:30 PM
> Subject: Re: [APML] New TP pictures
>
>
>> I can't see how either of those could cause this effect. Where you 
>> using a dewheater on your OTA?
>>
>> thanks
>>
>> Duncan
>>
>> joe wrote:
>>
>>> Duncan, I used to have that same 'single spike' on bright stars in 
>>> my old 10" LX-5 SCT too.  I'd guess it's something to do with either 
>>> the corrector plate or the light baffel...joe  :)
>>>
>>>
>>> "May You Go Among The Imperishable Stars"
>>>
>>> Joe Mize:     jmize@svic.net
>>> StarFields Observatory   http://www.cav-sfo.com
>>> Chiefland, FL    29:24'33.4"N    82:51'37.7"W
>>> Moon Phase:     http://tycho.usno.navy.mil/cgi-bin/phase.gif
>>>
>>> ----- Original Message ----- From: "Duncan Munro" <dmunro@sfu.ca>
>>> To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
>>> Sent: Friday, March 18, 2005 1:42 AM
>>> Subject: Re: [APML] New TP pictures
>>>
>>>
>>>> You can't beat techpan for it's deepspace "mood".  I really enjoyed 
>>>> the other techpan shots as well. I can't seem to find any info on 
>>>> David's equipment. I'm really curious to know what mount he's using.
>>>>
>>>> Also,I wonder what is causing the single spike effect on  the 
>>>> bright star in the M101 image. This effect is also present in the 
>>>> M81 image as well. I am getting a similar "single spike" effect 
>>>> with my 10" SCT and I suspect it may be caused by by dewzapper 
>>>> running at too high an amperage but maybe someone has an alternate 
>>>> explanation?
>>>>
>>>> cheers
>>>>
>>>> Duncan
>>>>
>>>> GARY HATFIELD wrote:
>>>>
>>>>> Nice shots David!  I especially like the M101 image.  Can't help 
>>>>> you on your question, I don't know either.
>>>>>  Gary
>>>>>
>>>>>     ----- Original Message -----
>>>>>     *From:* davidanna <mailto:davidanna@jazzfree.com>
>>>>>     *To:* Discussion of Film Astrophotography
>>>>>     <mailto:astro-photo@seds.org>
>>>>>     *Sent:* Wednesday, March 17, 2004 3:09 PM
>>>>>     *Subject:* [APML] New TP pictures
>>>>>
>>>>>     Hi list
>>>>>      I have posted two new TP images from last new moon, I hope you
>>>>>     enjoy them
>>>>>     BTW does anyone know the difference between Substract and 
>>>>> Absolute
>>>>>     Difference making compositions with Picture Window?
>>>>>      http://eureka.ya.com/astrophoto/new.htm
>>>>>      David Gimenez i Rocamora
>>>>>     Corbera de Llobregat
>>>>>     mailto:davidanna@jazzfree.com
>>>>>     http://eureka.ya.com/astrophoto/index.htm
>>>>>     No virus found in this outgoing message.
>>>>>     Checked by AVG Anti-Virus.
>>>>>     Version: 7.0.308 / Virus Database: 266.7.3 - Release Date: 
>>>>> 15/03/2005
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