Recent wide-angle DSLR shot

Limited opportunities to image this week, for several reasons.  Posting this image I took at 2130 last Saturday at a fairly dark site using my Canon 5D Mk II, and my 16-35mm f/2.8 zoom at 35mm focal length.  It was a 30 second exposure using my Skywatcher AstroTracker travel mount (ISO 1600).

Just labeled a few objects in the field of view for orientation.  With fewer clouds, the site should prove very friendly to some imaging in the future.  I think it's pretty, even with the under-lit clouds rolling in.

Comet PANSTARRS C/2011 L-4 (taken on 15 March 2013)

Just a quick post, its been a while since I've added anything.

Looking through some old files, I rediscovered an image I had taken with my Canon 5D Mark II when PANSTARRS C/2011 L-4 was at perihelion in 2013.  Image was taken just after sunset, from Seaford Virginia with a 0.8 second exposure on a 50mm lens at iso 640.  I like the trees in the foreground giving a bit of scale to the image.

PANSTARRS L-4 is a non-periodic comet, so no more chances to see this one.

I've been helping a friend with his observatory, so not much imaging of my own lately to share for now...

Abell 21, a planetary nebula in Gemini, also known as the Medusa Nebula due to the appearance of striations in the nebulosity resembling the snakes of Medusa's hair.
Taken on the night of 12-13 Feb 2019 at Whorley. I used my 5” Explore Scientific refractor with no changes to the configuration. Imaging encompassed 120 light frames of 30 seconds each across luminance, red, green and blue filters, equating to 1 hour of light data.  Full calibration data was taken after the lights as well. Significantly, this is my first full rgb imaging session to include autoguiding throughout the imaging. I did, at the time, feel the guiding was being overly aggressive, and that the RA axis was over-correcting. However, the finished product, with round stars required no deconvolution tells me the guide must have been okay.

The nebula is an old planetary, and considered to be dim (8” scope recommended...) Well, 5” works too apparently.

Processing of the lights and calibrations were all on PixInsight. Will describe that process in an update.

Regards,
Mark J

Horsehead Nebula - imaging and processing

Dark skies during last Friday's moonless night gave me a chance to work on imaging.  I used my 127mm Explore Scientific APO refractor with the Moonlight focuser, the QHY5III174 monochrome imager, my SSAG guider on the 80mm piggyback scope, all mounted on the Losmandy G11 mount and driven by SkyX Pro via my MacBook running Parallels.  Filters were the Baader LRGB 1.25" set, mounted in a Skyris manual filter wheel.  A previous-night QHY Polemaster polar alignment proved to remain pretty tight.

This is the result of fifty images per color and fifty more for luminance, also incorporating my guide camera through SkyX.  Finished up with 25 images each for Flat, Dark and Bias calibration.

Only 20 second exposures for each science image... I chose 20 seconds due to some issues I've been having with the GHY5III174 monochrome camera reading-out early, before the duration is over, on occasions where I set the exposure length longer than about 30 seconds.  Still troubleshooting that issue.

I found that the guiding plot chart on SkyX showed what I assessed to be too much correction in Declination axis when I checked during the first set of images.  This settled down very well once I decreased the 'Aggressiveness' setting for SkyX guiding.  I did not reshoot the images though, so I know I can improve results in the future.  I will work on improving my guiding optimization next time too, since R.A. guiding looked a bit rough harsh as well.

Processing the approximately 300 images was done via PixInsight.  I'm a newbie on using the software for anything more than a quick histogram correction, but after all day Saturday working through book 'Inside PixInsight' by Warren Keller, I'm figuring out a workflow to integrate, calibrate and correct monochrome images... next time it will be a lot quicker.  I'll write more about that process  later.

Lots more to learn on processing, but I'm ready to call this image presentable.  The size and framing of this image make it difficult to tell what parts of the diffuse glow is from skyglow and what parts are part of the nebula, so I limited my processing so that I don't unnecessarily remove actual detail from the image.

I plan to come back to this target once I fix my camera readout issues so I can get longer exposures and bring more of the color that is clearly visible here.  Thats all for now.

Mark J.

Solar Eclipse retrospective

I began my interest in solar eclipses shortly before the 11 July 1991 eclipse which tracked across Hawaii before crossing Baja California and Central Mexico.  At the time I was working at the Lunar & Planetary Laboratory (LPL) in Tucson following my graduation from the University of Arizona two months earlier.  Some of my colleagues were involved in an eclipse observation trip to the totality in Hawaii, and just the day prior to totality I committed with a friend to drive down to Mexico to try to observe it via hand-built pin-hole projection.  We got close to the path, however we diverted to a beach we knew a bit shy of the 100% line due to fatigue and didn't go any further on the actual day.  No photos were taken, but the love of the event took hold.

More to follow...  meanwhile, here's a picture from the 17 August 2017 eclipse, taken in Casper Wyoming with my portable telescope rig:

5-6 May 18 (a short post)

Successful calibration of the Auto Guider / mount pulse-guiding arrangement  The key issue with all my failed calibration attempts was the hot pixels on the guide camera.

I had never done Dark images for the guider, so all previous guide calibration attempts still had hot pixels on the guide images.  When running those previous calibration cycles, TheSkyX appeared to use the hot pixels instead of a star for calculating tracking rates.

Choosing a star field with very few stars for guiding, it became clear which area of the guide image was being used for calibration, and it seemed to be a single pixel.  This highlighted several consistent pixels across multiple images and made it clear what was necessary.  I processed an auto guide image for dark subtraction and subsequently had my first successful calibration.

With the guider / mount tracking rates calibrated, I can now work to optimize the guider settings.  Current settings:

min move 0.010 seconds

max move 1.00 seconds

aggressiveness - all are 10

results:

M13 60 second clear, guided image

More Galaxies

A few recent updates to the rig...  Current imaging setup:

Explore Scientific 127 APO triplet
Explore Scientific 0.7 Focal Reducer / Field Flattener
Moonlite Crayford Focuser 2.5"

Celestron Five Position Skyris Filter Wheel

Losmandy G11GT Mount

Orion short-tube 80 (F/5) for guiding

Orion Starshoot Autoguider (SSAG)

Explore Scientific 50mm finder

Thunderbolt 2 dock

QHY Polemaster polar scope

QHY5IIIM174 (for imaging)

Skyshed

Next purchase:

Narrowing down my selection for a new imaging camera.

Galaxies:

Captured M51 on the evening of 16 April.  One 4 minute exposure, calibrated with 4 minute dark and a bias image.  Missed the opportunity to get flat field images, so I used some old ones for processing, still pretty satisfied with the result for this unguided image.

M51

Another session last night (20-21 April 18) to capture galaxies.  Also unguided, but this time I did record some flat field images:

NGC4535

M94

Also, here is m81 and m82 in a 240 second exposure, also unguided:

Next session will be focused optimizing my guider parameters.  Looking forward to successful imaging longer than four minutes...



PS: a gratuitous waxing crescent moon shot: