Posts Made By: Alex McConahay

From Nightfall (Borrego Springs, CA), LRGB 25,30,20,15 (clouds and bad tracking took out some of the five minute subexposures, especially in blue). TV 85, TV flattener, G11, QSI 583, Maxim DL and Photoshop

Alex

Am I the only one in the world who has trouble with field flatteners/fpocal reducers on an SCT?

After having a few otherwise great shots ruined by lens flare while using a standard 6.3 compressor/field flattener on my C9.25, I decided to run a test. I borrowed three field such things from my friends (three Celestron, one Meade). I stuck them in the tube, pointed at the Pleiades, and got the following, from all four of them. And I often get this kind of thing when using a flattener. It appears to come from stars just outside the FOV, although I don't know if that is true. I have done all the obvious (looking down the barrel for anything shiny, etc.)

Oh, I should add that I do not notice it when using the scope at F10 (without flattener/reducer).

What is your experience? Is this a common problem. Is there a trick to using the field flattener/Corrector/Focal reducer that overcomes this?

Alex

I'm doing a presentation in the near future on "filters." I am looking for a set of pictures to show how they work. Specifically, pics of objects unfiltered, and then filtered.

Anybody have any idea where I can find such?

Alex

I'm just learning this narrowband stuff, and have not quite figured out the colors, but I was glad to see I could take something from my suburban home under a substantial moon last night.

Alex

Are you talking about the "All this knowledge...I don't understand" placed at 1:36 today?

Alex

Here is an effort from last week.

Orion Ha(Green) and OIII (Blue) with Shuler Astrodon SII (Red) then severely color shifted to remove green and replace with red.

About nine fifteen minute exposures of each on a TV 85/Gemini/QSI 583.

Alex

This month's full moon is about as big as it gets, since the moon is about as close at it gets.

Some time ago, I wrote an article about this phenomenom for our club newsletter.

You can find it here.

http://alexastro.com/Alex%20Home%20Page/Articles/Whythemoonisbig.pdf

Enjoy.....

Alex

(PS.....the moon is still not as big as Mars in August.)

Short form: Can I make a solar projection setup out of just about any telescope?

I mean without burning up the tube or eyepiece.

Long Form:

I have a real nice solar setup with rear projection. Works great.

I made it out of my first telescope, a 60 mm Bushnell. Cause I figure if it burned up, I did not care all that much.

Well, I was thinking of upgrading to one of my "real" scopes. I have several tubes that could be candidates. But before I let an unfiltered sun go through them, I want to know about some issues----

I have no concerns about safety. I designed this to use around kids. One would have to go way out of his or her way to get into a position where they could see the unfiltered sun. (And I have hundreds of hours working outreaches with elementary school kids and others--so I am really not worried.)

I am mostly concerned about my equipment, heat buildup, etc.

Is there any problem with just letting the sun go right through a sealed-tube refractor or SCT/Mak with a nice eyepiece? I imagine there is some heat buildup, but since the surfaces are reflective or transparent, it is not as if I am sticking a piece of paper (or an ant) at the focal point. I have not noticed any heat problems with my old Bushnell, but, well I am still reluctant to try it out with a good (expensive) scope.

What is your experience?

Alex

http://www.pentax.jp/english/news/2011/201107.html

Apparently a new Pentax uses the digital shake system to track the stars during a long exposure.

ANybody know anything about this?

Alex

Registration is open for the Riverside AstroImaging Workshop on September 16 in Pasadena, just before PATS. This is shaping up to be a real nice show, with Ken Crawford, Warren Keller, R. Jay GaBany, Wolfgang Promper, Tim Pickett, Rogelio Bernal, and Daniel Perry doing the presenting.

There is a lot going on. Details are at http://patsimage.org/

I've also posted an ad in the classified-- #741694.