Wednesday, February 20, 2019

Feb 19, 2019: Super Snow Moon

  What a Challenge between the appearance of the Super Snow Moon and the clouds that were appearing each night.  For a few hours, there were no clouds and I managed to get some good results.

Rising Super Snow Moon (about 10pm)

Rising super snow moon, Feb 19th evening


Almost Super Snow Moon (apparently because its February and snow is everywhere - except Florida)  February 19 about 3am

    
A sequence of the almost full moon setting Feb 19 about 3am.  The darker images are when clouds were competing for equal time   
 

Monday, February 11, 2019


February 6, 2019:  Understanding vignetting and post processing astrophotos

I've been plagued for months with the light region in the image (below).  I was using Deep Sky Stacker to produce the images and skipped the flat and bias images.  Turned out to be a huge mistake.   The flat images are obtained by shooting an evenly illuminated subject (sky, through a paper towel or tee shirt) at the same ISO used for the light (astrophotos) images.  The bias image are obtained by shooting a dark field with the lens cap on - typically 1/8000 sec, to measure the dark current associated with no exposure (hence the high shutter speed). Dark images are also taken at the same settings as the light images with the lens cap on.  This gives a measure of the dark current associated with the exposure and ISO used for the light images. 

This article discusses how to adjust for vignetting: Photoshop techniques to correct for vignetting




DSS image of NGC2024 and IC434 - I did not understand the white region in the middle
An image of the morning sky as seen through a paper towel covering the front of the lens

Stretching the histogram of the above flat image reveals dark corners - vignetting
Deep Sky Stacker corrects for vignetting (using the flat images) and here is the result - a stack of 150 images of NGC 2024 (flame nebula) and IC434 (horsehead nebula) - no highlighted area in the middle  


Another Example:   M31
 
M31 with significant vignetting
M31 with flat compensation followed by GIMP autobalance (histogram stretch)

February 10, 2019: Triple Creek Nature Preserve

Was a rainy night then stopped about 6am  - but I did not expect to find much due to the mild cold of winter.  I was surprised to find a Phidippus regius with a valentine heart on her dorsal aspect of her abdomen

Cuckoo Wasp - Folded 

Cuckoo Wasp roaming about my finger

Phidippus regias (?) emerging from her egg sac

New spider for me

Newly hatched spiderlings: A tangle of legs

Egg Sac hanging from a small twig

Hanging egg sac with recently emerged spiderlings

A patch of volunteer watermelons

This was hiding under one of the watermelons:  Phidippus regis

Looking at me

A valentine Phidippus regius - masquerading as Phidippus valentinas  - what a surprise!!!

Wednesday, January 30, 2019

January 30, 2019: Progress with post processing DSLR deep space objects

GIMP and processing astrophotographs

The main idea is to use levels to expand the histogram and "bring out" the features hidden in the almost black.  One way is to use Colors:Levels and move the center pointer to the right edge of the histogram, save and reopen moving the left pointer to the left edge of the histogram.  Repeat until you see the hidden features (this has the effect of expanding the histogram and moving it toward the middle of the intensity graph.

An alternate and easier way is to us Colors:Levels:All Colors: Auto Input Levels

Original Image of Alnitak with hidden NGC2024 and IC434

After processing with GIMP: Colors: Levels: All Colors Auto Input Levels

After cropping.  Auto Input Levels works magic to bring how hidden features
NGC2244:Rosette Nebula stacked

Single Frame NCG2244 with aircraft flyby
Rosette Nebula annotated by Astrometry.net
Astrometry.net annotation close
 
M31 uncropped

M31 cropped

Monday, January 21, 2019

Jan 20, 2019. Total Lunar Eclipse Sequence

Photos taken with Nikon D500,  Tamron 160-600mm lens @ 600mm, Tracking with a Starguider pro.