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Prime Focus Pleiades


Oct 25, 2000

 


----------------------------

#753 Oct 25, 2000

In a message dated 10/25/2000 5:12:27 PM Pacific Daylight Time, Herm writes:



< www.egroups.com/files/Losmandy_users/pleaides.jpg >>



Excellent! Are the double diffraction spikes the result of just slightly

being out of focus?



<

I was using an Orion STR80 refractor with my st4 and had inconsistent

tracking,

thanks to this list and Paul Sterngold and decided to try a barlow, when that

improved the tracking I went to an 80mm F11 guidescope...perfect tracking.>>



I'm confused...are you saying 880mm f11 guiding was a quantum leap over 800mm

f10 guiding while you were imaging at about 800mm?



>



How do you like this scope? Do you need/use a coma corrector? Thanks.



Mike Chapa



8" Celestron FASTAR SCT/ST-237 astroimaging webpage @

members.aol.com/mjchapa/astroimaging/main.html



----------------------------

#759 Oct 26, 2000

Yes, I was trying out a new 300LPI glass ronchi from Edmund's and it did not do

the trick..gotta always use a knife edge to check focus, its the only reliable

method at f4.



mjchapa@... wrote:

>In a message dated 10/25/2000 5:12:27 PM Pacific Daylight Time, Herm writes:

>

>< www.egroups.com/files/Losmandy_users/pleaides.jpg >>

>

>Excellent! Are the double diffraction spikes the result of just slightly

>being out of focus?

>



Herm

Astropics home.att.net/~hermperez



----------------------------

#800 Oct 31, 2000

mjchapa@... wrote:

><

>I was using an Orion STR80 refractor with my st4 and had inconsistent

>tracking,

>thanks to this list and Paul Sterngold and decided to try a barlow, when that

>improved the tracking I went to an 80mm F11 guidescope...perfect tracking.>>

>

>I'm confused...are you saying 880mm f11 guiding was a quantum leap over 800mm

>f10 guiding while you were imaging at about 800mm?



the 80mm f11 was a quantum jump above the 80mm f5 Orion Short Tube refractor, I

just posted a new version of the Pleaides shot on my web page, longer exposures

on E200 slide film. The Orion STR 80mm with the barlow worked too, but it was

more cumbersome... the 80mm F11 has better optics.

>>

>

>How do you like this scope? Do you need/use a coma corrector? Thanks.



Love it, yes you have to use a coma corrector..I use the Vixen one made for it.





Herm

Astropics home.att.net/~hermperez



----------------------------

#23431 Dec 12, 2004

I dunno about *you*, but my G-11 works fine, and I had my first

experience doing prime focus deep sky photography with it last night.



We don't get many clear nights in this part of the world, so when it

looked clear last night I packed up the gear and went to a local dark

(-ish) sky site. Just in time to se it getting a bit murky overhead,

but since i was there, I figured I might as well at least get in some

guiding practice.



For polar alignment I just dialed in Polaris and Delta Ursae Minoris

in the polar scope. For a first time out I wasn't going to be doing

much more than 5 minutes at a time, so field rotation was a non-issue.



The Pleiades were high in the sky, so I used them as my test subject.

For a telescope I used my 5" f/8 Synta achromat, with an 80mm f/11

scope from Apogee Inc. as the guide scope. Figured the Pleiades would

nicely fill a 35mm film frame, and they did.



Held the whole mess together with a couple of Losmandy DUP dovetail

plates, a couple of Losmandy guide scope rings, and some creativity

from the local hardware store. The guide scope didn't produce the

greatest images with a 12mm crosshair eyepiece and a 2x Barlow, but I

didn't need great images. Not from that scope, anyway. It's actually

quite good with more sensible eyepieces...



Being gnerally obstinate about these things I guided by hand (the

occasional nudge was all it needed), shot on film (Kodak Porta 400 UC,

because it was at the top of the pile in the fridge), developed the

film myself, and did some prints tonight, which are now hanging drying.



The results? Nice sharp stars, limiting magnitude about 13. Very

strange colour balance that I couldn't quite filter out in the

enlarger, making the stars look like they're class F or G, rather than

the O they're supposed to be (haze, perhaps?). A hint of the usual

nebulosity. If you look very carfully you may be able to convince

yourself the stars farthest from the centre of the field aren't quite

as round as those in the centre. It's not an apo, but it's awfully good.



We now return to our regularly scheduled series of calamities.



...laura



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