Thursday, August 30, 2018

Lynds' Dark Nebula 673

Lynds' Dark Nebula Catalog Numbe 673 in Aquila

Stellarvue SV4 Apo telescope at 653 mm F 6.3
QSI 683 with Astrodon filters

Blue x 19 @ 900 seconds
Green x 17 @ 900 seconds
Red x 18 @ 900 seconds
Lum x 26 @ 900 seconds

Taken during the Golden State Star Party in June 2017 & July 2018




Been a long time getting around to finishing these pictures.  I know that the color is a bit over saturated.  It's color balanced on the dark lanes of the dust clouds. 

This has turned out to be an interesting experiment in processing to show the absence of light.  Because the object of interest is so dark, I found that getting extra data was required, especially under very dark skies.  Thus, I found that I had to concentrate on this target only at GSSP.

Happy to finally be finished with this target, I'm ready to move on.

Thursday, August 9, 2018

Focus Confirmation

Checked and Double Checked


As mentioned in an earlier post, I've been working through the steps to properly measure infinity focus with the Pentax 67 400 mm EDIF lens.

I've been able to properly measure and confirm that the lens will reach infinity focus and that the Stiletto device is properly calibrated.

Monday, August 6, 2018

Measuring Infinity

Calibrating for infinity focus


As mentioned earlier, I've noticed a deeper issue with the ability to get good images out of the Pentax 67 camera when using it with the 400mm EDIF lens.

I decided that the next major step would be to use a knife edge or ronchi screen device to properly figure out the right settings.

Back in the day, I'd purchased a Stellar Technologies Stiletto IV device to help find perfect infinity focus.  The company has since folded as the digital age with bahtinov masks and live view has rendered needing to pre-focus unnecessary. When I first got the product, I thought that I'd be able to use my 35mm K1000 to get some pictures.  However, I never did this, instead I jumped straight to playing around with short exposures with a digital camera.  By the time I got a DSLR, the Stiletto had become obsolete.  I'd tried using it a few times and was disappointed with the way that the focus looked.  I eventually put it away and moved on with other activities.

Friday, August 3, 2018

Ektachrome at GSSP 2018

Film astrophotography is not dead!


During the recent star party, I collaborated with Isabell Lin De La Cruz and worked through some targets on film.  She added her Pentax 67ii body to the tracking setup that I've been using and I swapped out the second 400mm lens for the shorter 165mm lens.

Because the darkness at this location in northern California is limited, I'd modified the estimate for exposures to use 40 minute durations at F4.  This meant running the 400mm EDIF wide open - a big risk.  On the other hand, it would be a cakewalk for the 165mm f2.8 lens.

The weather during the star party varied.  Some nights were clear and others had high haze.  All had good darkness and few airplanes, just that when the clouds came in, there were no stars!

We also shot some Portra and haven't gotten that developed yet.

I sent the Ektachrome film off to The Darkroom to get it developed and didn't preview the results until I had the film back in my hands yesterday.  When I saw them, I was pleased at the exposures and was glad that we'd opted for the settings and push.

When I did the deep scans on the Plustek Opticfilm 120 (5300 dpi) I found that all the images from the 400mm lens are out of focus.  This is frustrating, but expected, because even though we used the loupe and young eyes to check focus, I think that there's a need to do a more precise focus.  It may be time to learn to use a knife edge or ronchi grating (I have both).

The 165mm lens really shined.  Stars are crisp and there's very little vignette.


Cropped frame of M31

I've already scanned the rest of the images from the roll.  Will be uploading more.