Getting to 0.63X part 2

I did manage to image M42 from the terrace at around 2AM with the filter in place and with a focal reducer sensor distance of 110mm. This configuration gives a 0.62x reduction. On a self induced downer I selected the 3104 pixel instead of 4144 pixel format thus robbing myself of knowing how well flattening occurs out to the farthest edge of the sensor. 

The processed image for an averaged series of 15s exposures follows. There is some coma evident in the stars in the upper right corner. However some star elongation due to guiding errors is also evident. Polar alignment on the terrace is fairly crude proving quite challenging to the auto-guider. 

M42

A note about post processing: This series of overnight M42 exercises has allowed me to greatly simplify my post processing. I use Paintshop Pro X9*. The above image was achieved in three or four steps with the first step a script that I will outline in the next post. 

* I recently upgraded to Paintshop Pro 2021. I'll talk about that in a future post.

Getting to 0.63X --- yes M42 again!

Until now I have been imaging at ~0.40X using the diagonal between the camera and the focal reducer or at ~ 0.72x using the adapters and spacers supplied with the ASI294MC-Pro along with the SCT threaded coupler from the diagonal. To get to actual 0.63x, presumably the optimal focal reduction for best field flattening the spacing between the focal reducer and the sensor needs to be about 106mm based on the calculation found here.

Luck would have it I happened to have an eyepiece projection camera adapter tube of just the right length and threading for a back plate opening. Unfortunately, because clouds were moving in I only had time for one round of 35 x 15s  shots with M42 still partly blocked by tree branches. Nonetheless the exercise was valuable. There's plenty vignetting that could be largely eliminated via flat frame correction. Also, because this was shot from my terrace tracking was sub-optimal despite the use of the auto-tracker.

 
Update: The camera adapter configuration in this above posting provides no provision for using a filter. Luckily, after a little experimentation I found a combination of adapters that can include a filter about halfway between the focal reducer and the sensor. In this configuration the sensor focal reducer spacing is about 110mm resulting in a 0.62x focal reduction. This setup still needs to be tested. Another M42 anyone? ;-)

Another 5AM Orion Nebula

Similar to October 22, I decided to image M42 from my mostly tree blocked patio at 5AM in what amounted to a practice session. Ultimately I want to acquire an M42 good enough to enlarge, frame and wall hang. Similar to previous patio adventures the scope was rough aligned the night before on Mars and three other stars; two for calibration the put in hybernation. I was awakened by the flip phone alarm at 4AM well before M42 cleared the #%@&ing tree.

I decided to image at the ASI294MC Pro's full frame, 1x1 binning and at 120 gain. I would use the best frames from sets of 30x15s and 30x30s. Cooling was set at -10C. I not aggressive in cooling to limit taxing the cooler and the battery. Flat frames were acquired later in the morning after the scope hand warmed up. Stacking with Autostakkert!3 and processing with Paintshop Pro 9 resulted in the following.

Not bad. I don't consider this quite frame worthy but it's close. The problem is the haloing around the bright stars which might derive from my use of a light pollution filter just in front of the camera or from the protective glass in front of the sensor. That said, I'm really impressed by how well the auto-guider does considering my rough alignment on the patio. I really look forward to a few rare mid Atlantic clear, moonless nights with good seeing where I can go to one of my darkish sites to put this system through its paces.

5AM Orion Nebula

Waxing gibbous moon, poor seeing and sketchy clear sky forecasts offer few reasons to head out to the park or to my favorite darkish sites at Harvard Massachusetts or Myles Standish Forest.  I decided to image M42 from the patio at 5AM. 

Scope was setup using two alighment and two calibration stars to get some pointing accurace. No ASPA polar align of the AVX mount was performed. The hard guiding work would be the onus of the auto guider. 

I woke around 0330 EDT to early to start imaging so I listened to a couple of podcasts until 0445 when M42 would be close to clearing the #@%&ing tree in front of my patio. This would be a practice session to further familiarize myself with the Orion Magnificent Mini Auto Guider.

After reawakening the mount from hibernation mode from last evening's setup I slewed to Rigel to check pointing accuracy. Rigel was spot on in the center of the ASI294MC Pro sensor. I slewed to M42, fired up the auto guider, tweaked the guide scope focus and did a PHD2 calibration. Calibration took less than 5 minutes.

For fun I decided to layer sets of 25x2 sec and 25x8 sec exposures and experiment with local tone mapping to expand dynamic range. This is new to me largely because most astroimaging howto articles focus on Adobe Photoshop or occassionally on freeware Gimp. I use Corel Paintshop Pro X9. One result follows. Bummer that the star to the right intruded with stray light. However, there will be plenty of M42 opportunities over the next few months. 

M42

Auto Guider night three

Forecast for tonight was increasing clouds but there was a clear window of opportunity between sunset and 9 PM. I decided to take another practice shot at M22. I set up the 8" SCT AVX on the patio the same as last night, i.e. single star alignment on Saturn. Like last night there was plenty of drift, mostly in declination. 

My first attempts to calibrate on a star near Saturn started giving the 'star did not move enough' error like last night. Goof one: I forgot to plug in the mount guiding cable. Even with the cable plugged in and checking the settings the auto guider  kept failing to calibrate.

A quick Google search on the error turned up  an old  Stargazers Lounge posting suggesting I increase the 'step size' from 500 to 1500. That worked. It took about 5 minutes to complete calibration at which point I acquired the following M22 image stacking 16 x 15sec exposures.  Of course the goal is exposures in the minutes range with filters. 

Auto-guider Night Two

It's been mostly cloudy since the beginning of October limiting my skygazing and auto-guider familiarization. Last night I finally was able to put it all together.

The test was as tough as it gets. My second floor patio is pretty useless for skygazing with all the trees blocking my view except for a narrow ~ 15 degree opening to the south. The patio overhang blocks the sky above. Despite, my lack of access to Polaris, my rough alignment with north,  I managed a single star alignment on Nunki with the Celestron AVX using the AVX Quick alignment.

The forecast was for mostly cloudy so it was imperative I use whatever clear sky quickly. I slewed over to and centered M22 on the ASI294MC Pro sensor. A bright star was selected, the PhD2 button was clicked and calibration begun. With the F/6.3 focal reducer and diagonal EFL was calculated to be 880 mm. For this first try it became evident the guider was not tracking with considerable drifting by M22.

After a few stumbles with advanced settings I started getting a 'star moved too little' error. I reviewed the advanced settings in the help files which are pretty good. I had inadvertently unchecked the Enable Guide Output ... oops. Enable Guide Output box checked calibration went smoothly.

M22 had moved behind the trees by the time I corrected my errors. I slewed to and centered M75. Auto-guider calibration went quickly on the selected star and auto-guiding started. Focusing was not the best on either the imager screen or the auto-guider screen. Nonetheless tracking was spot on for a series of 8, 15 and 30 sec sets of 25 subframes. Great performance considering the mediocre conditions.

Fingers crossed, the forecast for Saturday is for mostly clear night skies. My hope is a good workout for this great little device at one of my darkish sites.

Orion Autoguider first night out.

In my last post I mentioned I had ordered an Orion Magnificent Mini Autoguider Package. It arrived early Friday afternoon giving me time to quickly unbox it, scan the instructions and familiarize myself with the device. The package consists of the auto guiding camera, a 50mm guide scope, mounting hardware and cables. 

I decided to head to Harvard, MA gambling on a better sky than my local park. I should have stayed local, saving the gas, because the sky was pretty clear when I return around 1AM. My goal for the night was to align the guide scope, do a calibration and image a couple of DSOs with guiding. Things did not go as planned.

Because the guide scope and the main scope were so far out of alignment it took me more than an hour setting up the scope hooking up the cables and using Polaris as a target aligning the guide scope with the finder. Complicating matters is sometimes the guide camera acts a bit flaky in how it normalizes the view. If  a star is present the background becomes dark. However, sometimes when the cap is on the screen would go completely white. In any case I did manage to get the guide and main scope aligned. 

I had considered using the guide scope as the finder on imaging nights. Unfortunately the flashing red LED on the back of the guiding camera makes it difficult to sight along the guide scope to aim at a bright alignment star. Thus it took my almost 3x longer than normal to do my usual 2 alignment star, 4 calibration star and all star polar alignment Thus the reason for re-installing the 6x30 finder scope. 

Once aligned I decided to test the scope on a globular cluster; as usual M13.  I goto pointed the scope to M13 and centered it. Here's where the night fell apart. The quick start instruction is to select a star near the middle of the auto-guider screen. If the box around the star is green your ready to go. Then you press the PhD2 button to start the process. Unfortunately, in my case the the PhD2 button was grayed; i.e. disabled. An indicator at the bottom of the view showed no scope selected. 

Hmm. I searched around the menus for whether there was some setting I missed but did not find it. I began to wonder if there was a problem with the clock drive. With clouds starting to move in a the Schmidt cassegrain corrector plate starting to fog from dew I packed up for the night and for the hour drive home. 

In the morning thanks to a 2015 thread by PHD2 enthusiasts I figured out the problem. You connect the camera via a dialog  where you also connect the mount. However the 'mount' is actually on the camera. But the mount selection was grayed out. It turns out I needed to connect all. Doh! PHD2 actually stands for 'Push Here Dummy.' I really did feel a bit dumb after last night.

Light Pollution Filter

It's embarrassing but I have had this Orion Light Pollution filter for a number of years for use in visual DSO viewing. Never, thought to use it with my previous or current deep sky imagers until last night (9/30/2018). My doh! moment came while watching an AstroBackYard Youtube video review of the ASI294MC Pro where the narrator admires the sensitivity of the camera even with filters. 

The images below were acquired using with the Orion LPF in heavily and increasingly light polluted Frederick Maryland. M27 was acquired using 15 sec exposures at using a Celestron 8 at F/4.6 on an AVX mount with tracking but no autoguider. The two nebulae were the same configuration but 30 sec exposures.  My near term goal is to acquire an autoguider and increase exposure times.

Messier 27

NGC6888 Crescent Nebula

NGC6992 

Update: I just ordered an Orion Magnificent Mini Autoguider. To date I have never imaged with guiding and it pretty much shows when images are enlarged. The stars are almost always a little misshaped or elongated for exposures longer than 15 sec. I've been content to tolerate these flaws.  The Celestron AVX tracks beautifully for it's size and weight but no mount is perfect. With the ASI294MC-Pro its time to go deeper with longer exposures with the additional benefit of guiding.

A few ASI 294 MC Pro Images

Before getting into the imaging it's valuable to note that ASI294MC-Pro was not recognized by SharpCap 2.9 forcing me to upgrade to  v3.1. To benefit from live dark frame subtraction I had to pay for the pro version only to find the dark frame subtraction did not work properly. I noted this to the developer who has worked with me to fix the issue which I'm currently testing. Recently, clear skies have been the exception. The following images were acquired without the live frame subtraction with dark frames applied during  Autostakkert processing.

Messier 17

Messier 16

Messier 22

Messier 27

Except for the exposure times all of the above images were averaged from 25 subframes using the following settings.  Messier 22 was acquired using 8s images. The other three images were acquired using 15s images.

Well...the ASI174MC-COOL did not work out

Ignore the publication date. This post was written around July 20th, 2018 but only published 8/8/18. I'll try for brevity.

The ASI174MC-COOL camera that replaced my mothballed but still working Meade DSI Color died TWICE under warranty. I suspect this was due to the camera drawing too much current and overheating while acquiring dark images for later use. When it worked the camera was productive and enjoyable to use despite its high amplifier glow. High Point Scientific was classy enough to  issue me a credit for the full camera price after the second failure. Thank you HPS.

I used the credit, plus an additional $311 to procure the popular ASI294MC-Pro. I've only had it a couple days but so far am impressed. I was inspired to get the 294 by the awesome Astrobin images taken by Robin Clark with herv14" Celestron Edge SCT with a 0.67x focal reducer. Although her imager is an ASI1600MC-Pro its pixels are a bit smaller suggesting the ASI294MC-Pro is a bit more sensitive.

I use an 8" Celestron SCT also with a 0.67x. Suggesting the 294MC Pro would be a good match. To my delight on my second night out with the new camera I was able to get this M-13 image, though sadly marred by a dust speck ring.

Update: I was not using flat frames at the time of this writing.

The image is also noisy as I was running at high gain and with short (8s) exposures and dark frames only averaged from five sub-frames. 

Early Messier 13

For this early Messier 13 I used the live stacking feature in SharpCap 2.9. While convenient must remember to save the image "As Shown" to get a color image. I also used temperature control (15C) in this case. The high temperature is because I was being conservative with battery usage and also trying to keep the temperature above the dew point.