From: Mark Gaffney <markgaffney@me.com>

Date: February 10, 2010 9:57:24 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Scorpion Sun Images...

Alan, 

By the way with one eye closed the solar film over the end of the finder was a very quick way of locating that disc, otherwise elusive with the smallest shadow. (I`m thinking I`ll have to make a holder for the film out of a bottle cap to go on the end of the finder?) Smallest shadow is a good basic start though for being close enough. I am also locating it with the eyepiece when it`s somewhere near centre. I`ve just found Hist Expand. Where should it be set;  Auto or once? It`s a guide only when processing later though, is this the case? It dosen`t seem to alter anything in imaging though by what you`ve said I may be wrong. I`ll have a look in the Manual later. These marks on the glass are, I think the residue of my cleaning with a small amount of detergent in water & not dust motes- again I may be wrong but I can`t see any motes at all on the glass when looking just now....Just before I was in the house & writing on my iPod so couldn`t refer back readily to the text of your message..I don`t have any lesions on my eyeballs that I`m noticing but a case of sunstroke definitely...!Thanks,

Mark.

On 11/02/2010, at 2:28 PM, Alan Friedman wrote:

Hi Mark,

A couple of suggestions;

1. Get an observing cloth. I use a piece of black polar fleece with a silver fabric sewn to one side to reflect the heat. It covers my head when I am doing visual observing, and my head and laptop when I am capturing solar data with Astro IIDC. When selecting a piece of cloth, choose something supple and hold it up to a light bulb to make sure it isn't too sheer.

2. Your focus is off - I can tell that by the fact that your dust motes are as close to focus as the sunspots. Dust motes are always a problem with these sensors. You should have a can of compressed air for photographic use. You can use it to blow dust off your optics and off the chip of your camera too. Just be careful not to shake the can and point and release some air at your hand right before cleaning to be sure that no propellant is being released.

3. Get the exposure right. Use the histogram in AstroIIDC to ensure that you are not cutting off data at the white end. Your image is mostly blown out in the whites. When properly exposed, the solar disk should have tone throughout - no white. You can adjust the levels afterward if needed, but you cannot put back what was not recorded in the first place - in the case, the detail in the brightest sections of your image.

4. You really want to master the technique of finding the sun by minimizing the shadow. There are also some finder scopes made by Televue and others that work from a cast shadow. You don't want to be sighting towards the sun to locate it in the scope. A couple of quick glances and you'll have lots of nice spots in your eyes that take time to go away before you can see the laptop screen again.

5. Don't use ROI... there is no advantage for you. You don't need to average many if any frames when imaging the sun - you can shoot it with 0 gain (brightness) so the individual frames will have lovely signal and very little noise. Most of my recent solar images are constructed using single movie frames without any stacking at all.

practice... practice - it's summer!

best,

Alan 

On Feb 10, 2010, at 8:10 PM, Mark Gaffney wrote:

You guys have been busy whilst I`ve been doing this! These Suns are
shot with a Scorpion 20SO mono camera using Baader solar film & my
C9.25 scope at prime focus. The camera is set to 814 x 618 pixels
ROI...I think for the 2nd of these I went to 30 fps, the first one was
at 15 fps & using very minimal exposures .90 ms for both, I think. I
have to put my lap-top over a bit under a bush & a good few feet from
the scope or I can`t see anything because of glare ( we don`t have a
useable beach umbrella at present..) so focusing is very difficult
(not to mention co-inciding this with getting an acceptable exposure.
(thank goodness there were no march flies this time..! -I had some
Aeroguard & there were less around-also I remembered to wear a hat but
it was still very hot especially by the time I was ready to give
up! ). I found a useful expedient was to put a small corner of the
solar film (about 1 inch square) over the front of the finder. I spent
ages before this trying to simultaneously locate & focus the Sun-using
smallest shadow etc.... I don`t know how I`m getting these blotches on
the glass cover of the chip..the camera is covered except when I take
the grey PGR cover off to test something? I certainly don`t have time
when all set up at the scope to be cleaning cameras, especially with
the Sun which has a limited time it can be imaged because of the heat!
But it`s probably spoiled these images for what they`re worth. Lastly,
I`m finding a single sharpest frame seems to be the best option for
clarity...& I`m only posting them as small size attachments here.....
Mark