July 20, 2022 Summer Favorites

All images were acquired with Celestron 8 SCT on AVX mount with ZWO ASI294MC Pro using Starizona Night Owl operating at F/4 and light pollution filter.  Subs for the comet, Sh2-142 and Sh2-155 were 30s typical for the Harvard, MA area. I'll revisit the Sharpless targets with 60s exposures in the future to try to bring out more nebulosity. Exposures respectively for M27(my better half's favorite)  and M13 were 8s and 15s. Update: M13 reprocessed for better contrast. 

M13

Comet C2017K2 PANSTARRS

Sharpless 155

Sharpless 142

M27

Globular Clusters

This is the time of the year to image globular clusters, some of my favorite targets. The bulk of them tend to be low in the southern sky which is a challenge considering seeing and refraction. M13 was included in the previous post. Several others acquired on the same night appear below. M55 was acquired on a later night. Images were averaged from 30x30s subframes acquired at 120 unity gain. Configuration was Celestron 8 , Starizona NightOwl 0.4x focal reducer, ZWO ASI294MC Pro CMOS camera. Update: Images reprocessed with GraXpert stretching and residual gradient removal.

Messier 3

Messier 4

Messier 5

Messier 10

Messier 12

Messier 13

Messier 55

Seasonal Favorites

It's that time of the year, mid summer, to revisit old favorites. I never tire trying to better myself imaging these or other targets. All my recent imaging has been done from increasingly light polluted Harvard MA. Poorly targeted and excessive LED lighting is really trying to kill off night. Nonetheless the Milky Way can still be glimpsed overhead from Harvard. Typically 30 to 60 30 second exposures are acquired at F/4 using the Starizona Night Owl focal reducer corrector, light pollution filter and ZWO ASI294MC Pro using 120 unity gain. Subframes are stacked and averaged with Autostakkert! 3.  Images histograms stretched and images processed in PaintShop Pro 2021. Additional processing done in using Microsoft Photos bundled with Windows 10. 

IC5146 - Cocoon Nebula

Messier 8 - Lagoon Nebula

Messier 16 - Eagle Nebula

Messier 17  - Swan or Omega Nebula

Messier 20 - Triffid Nebula

NGC7023 - Iris Nebula

Messier 13

NGC7380

NGC6992 Eastern Veil Nebula

Into Spring

Spring has arrived, so I've decided to get a jump on galaxy season. One non-galaxy target, overlooked by me in the past, is the gaseous nebula NGC2174. It was during an earlier open cluster imaging night that I noticed its nebulosity while imaging its associated open cluster NGC2175. Imaging wasn't under the best conditions, the heavily light polluted count of Frederick, MD, so I'll likely revisit NGC2174 in the future. It appears below along with five galaxies. All imaging was done at F/4 with a Starizona Night Owl focal reducer/corrector. Am, I glad I acquired this accessory before the SARS Covid-2 pandemic as it's been out of stock for months.  NGC2174 and NGC2175 were averaged from 60s sub frames. The galaxies were averaged  from 120s sub frames.

NGC2174 (gaseous nebula) and NGC2175 (open cluster)

M94 (galaxy)

M106 (galaxy)

M109 (galaxy)

NGC2403 (galaxy)

NGC2841(galaxy)

Better night than expected - 08/20/2020

Thursday 8/20/2020 promised to be clear night with average seeing according to Clearsky Charts and NOAA. I decided to head for the Harvard library darksite with the goal of imaging the Crescent, the Eastern and Western Veil nebulae using the Starizona Night Owl gambling on 120s sub frames at f/4. That proved a mistake. The results were under exposed and noisy. I won't bother posting the images here. In the future I will try imaging with 300s sub frames that yielded better results at a higher f/6.4 focal ratio in the past. 

Fortunately, I also imaged Comet Neowise, M8, M16, M17, M20 and M13 on the same night. Sub frames were acquired with 30s exposures at a gain of 120.  The images appear below. The images are pretty okay but could be  better. The auto-guider was quite erratic along the RA axis resulting in elongated stars. With the waxing moon I will focus on debugging this issue locally starting with running the PHD2 setup wizard. 

On a different note flat frames captured during twilight were at the wrong focus making them useless. I decided to keep the optical assembly together and collect a set of flat frames at home next day. The first set, taken from a lamp illuminated wall looked good but yielded ugly images marred with gradients. At first I assumed the problem was camera settings and light pollution. On a whim I tried using a white jpeg image on my LED HDTV screen as a flat frame target. It worked resulting in the  images below. 😊

Comet C/2020 F3 Neowise

M8 (Lagoon Nebula)

M16 (Eagle Nebula)

M17 (Omega Nebula)

M13 (Hercules Cluster)

M20 (Trifid Nebula)

So Begins Globular Cluster Season.

Globular clusters (GC) are some of my favorite targets for this time of the year with short spring and summer nights and the annoyance of daylight saving time. With sunsets around 2030 and astronomical twilight's around 2240 globulars can usually be acquired in less than 15 minutes making for productive nights of imaging. 

Why do I keep coming back to these low hanging fruits? I like to think I can improve on my past performance and take advantage very rare good seeing Northeast nights. Most of these targets are low in the southern sky making it challenging to image them with the denser more turbulent air and refraction.

A few recent examples appear below. All of these globulars were acquired from a favorite Harvard, MA darkish site with 15 x 30s subframes with a ASI294MC-Pro, Starizona Night Owl 0.4x focal reducer and Celestron 8 on an Advanced VX mount. 

While I call this Globular Cluster Season there are many more  open clusters favorably placed this time of the year. Look for images of those in up coming posts. 

Messier 3

Messier 5

Messier 53

Messier 13

Messier 92

NGC5897

Messier 4

Messier 10

Messier 12

Messier 14

New Starizona Night Owl Focal Reducer -- Updated

For some time I have used the combo 0.63x focal reducer(FR) and diagonal to achieve about an f/5 focal ratio with some rather distorted stars out to the edge of the ASI 294MC Pro with its 16x13mm sensor. Recently I procured a Starizona Nightowl FR which promises .. "to provide excellent image quality over a 16mm image circle." This is a bit of an over promise. Even near the 13mm dimension edge of the ASI294MC star distortion is quite evident; albeit less objectionable than the aforementioned 0.63x FR optical configuration. 

A bigger concern is uneven background vignetting. This is expected in any optical system which is why flat field correction is essential. However, in just my short experience with the Night Owl there is a small residual greenish glow  evident in the center of the Horsehead Nebula and NGC1981 images even after applying several flat fields acquired at different exposures. Imaging was from  a quite light polluted area, Frederick, Maryland and it's hoped a Orion SkyGlow Astrophotography Filter will help with this. Meanwhile here are a few early results. 

Update: Since this writeup almost all NightOwl images have been acquired at 3104x2116 or 3104x2844 pixel formats. At these formats flat frames are effective eliminating the residual greenish glow in the center of DSO images. I now do all NightOwl imaging at the 3104x2844 format. 

Barnard 33(Horse Head Nebula), NGC2023, 

NGC 2024(Flame Nebula)

Sharpless 279, NGC1981