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By Gary Shaw
I just acquired a 200mm F4 newtonian from TS Optics which I'll use primarily for Electronic Assisted Observing with several ZWO cmos cameras.
My challenge is that my current scope is an F3.6 schmidt newtonian so I have no experience with coma correctors or spacers/adaptors in the optical train. TS tells me that I need 55mm from the coma corrector (TSGPU) to the sensor. They provided 40 mm of various adaptors and spaces and I guess I get the remaining 15mm from the camera housing itself - as shown in the attached image. The threads on several of the adaptors(see notes) are bad so those pieces need to be replaced but, once that's fixed, I have four questions for this community:
1. ...is this odd assortment of parts and pieces typically how one goes about achieving the required 55mm dimension from the Coma Corrector to the camera sensor? Just seems that there must be a simpler, and sturdier way to do this without having to use 4-5 separate parts.
2. Once all the adaptors add up to the correct dimension and are attached to the Coma Corrector, where does one locate the whole assembly(with coma corrector) in the focuser draw tube? Is it a matter of trial and error?
3. If one did not care about viewing peripheral stars looking a bit like comets and didn't, therefore, use the coma corrector, would any of these adaptor/spacers be needed to bring the camera to focus so one could observe using, say, Sharpcap 3.2 Pro or other software?
4. If I were to use a filter or two, where would these best be located in the lineup and do they work with the various threads and adaptors?
Apologies for my lack of experience and thank you for any help you can provide me in understanding how to observe and image with coma correctors
By Cosmic Geoff
On 25th March I tried some live stacking with Sharpcap and a 102mm f5 Startravel achromat & ASI120MC camera.
Mount was Celestron SLT on custom tripod. Image size: 1280x960.
With this setup it is possible to dial in an object to the GoTo and be confident that it will appear on the laptop screen.
These images may not look too exciting but they do mimic the FOV and general appearance as seen in a 203mm SCT with 25mm EP. Check the image for M87. When I checked the field in Stellarium I found that two faint non-star smudges matched with NGC4478 and NGC4476, which are 11th and 12th mag galaxies. I am gob-smacked that I managed to image these with such modest equipment from an urban site. There is no way I would be able to see these visually even with a C8 from here.
I wasn't sure where to post this tip....it is probably of most use here....
Many of us with observatories or indoor Mission Control use Windows 10 Pro Remote Desktop to control a scope side computer running camera and scope control software from a second computer indoors. This works superbly at 1080p resolution.
However, I have struggled for a year trying to perfect a wireless solution that works with 4K UHD cameras terminating in a 4K UHD display. Until now, whilst cat 6 cable does work fine, wireless even at 5Ghz 802.11ac has struggled with some lag and poor performance. I have spent a fortune upgrading wireless adapters and range extenders, but this isn't the issue!
Here is a solution;
1. Seperate your dual band network into distinct 5Ghz and 2.4 Ghz channels.
This is easy with (say) a BT Home Hub. If you don't do this, it can be a bit hit or miss whether your 5 Ghz wireless adapters connect to the right channel. You will now see TWO channels, one at 2.4 Ghz with a suffix like <hub name> and another at 5 Ghz named <hub name -5>. Connect your 5Ghz adapters to the latter. If your internal adapters are merely 2.4Ghz, you can disable them via Device Manager and plug in a USB version costing around £5. Note that at 5 Ghz wireless range might drop. If so, a Netgear EX8000 wireless extender is recommended as it employs 'mesh' technology.
2. ONLY if you have a fast network, and powerful CPUs and quality graphics card, try DISABLE 'RemoteFX compression' in RDP.
This allows uncompressed screen data to flow across RDP. I have found this improves performance whether using 802.11ac wireless or cat 6 cable. What RemoteFX compression appears to do is limit effective RDP speeds to under 10Mbps (due to translation times). That is crazy if you have 433 Mbps adapters, and an 802.11ac network (or catv6 cable). Unleash the beast! Send across uncompressed data! The issue is not with speed or bandwidth, it is an artificially imposed limit in RDP.
To do this type 'Edit Group Policy' in the Windows 10 Pro search box (doesn't work in Win 10 Home). You need to drill down through about five levels of Windows Configeration Folders, and Administration Templates and Remote Desktop Services/Host folders to find a utility named <Edit RemoteFX Compression>. In that, your options are <disable> compression or <enable> a compromise mode.
If you don't know how to do this try Googling 'Disabling RemoteFX Compression' to find a lengthy Microsoft tutorial. Or visit https://docs.microsoft.com/en-us/windows-server/administration/performance-tuning/role/remote-desktop/session-hosts .
I deliberately don't here state the quick route sequence to access this deeply embedded network utility command because you are delving deep into developer/administrator territory and do need to understand what you are doing and how to revert to your original RDP settings if your network can't handle these levels of uncompressed screen data. We don't want any novice attempting this on a cheap Compute Stick on an inadequate network!
3. When employing RDP from your computer indoors, select <WAN 10 Mbps> or <LAN 10 Mbps> as appropriate via <Options><Experience>. The default <auto-select my connectivity> often selects too low an option. The irony here is you can select this and still not enjoy faster speeds unless you have edited/disabled RemoteFX compression.
I now have Atik Infinity plus CPWI software running in an end to end 4K UHD system terminating in a 4K UHD monitor. Over 802.11ac wireless it is now rock steady. Over cat 6 cable my system is now turbo powered. If you don't need RemoteFX Compression, don't let it restrict your network performance. It is evidently set to ensure it works on lowest common denominator networks. If you have a fast network/CPU, disable RemoteFX compression and finally release the beast of 4k UHD over RDP.
After a fistful of stars from the other night here's a few stars more from last night . Transparency was poor, though and I had to give up in the end. As well as fitting the Lightwave 0.8x to my 80 mm F6, I've also transferred the scope to the Heq5. Although I think Sharpcap is great for live stacking it won't always detect enough stars to auto align which means I have to use guiding. I can see plenty of stars on the screen but Sharpcap refuses to share my view! I've tried noise reduction and boosted digital gain etc. I think I'll try the v3.2 beta. I might try without the uhc in future as it probably cuts out too much light when combined with the IDAS D1. All live stacked with darks and flats. Some were guided.
M35 - 20 x 30s with IDAS D1 and UHC:
NGC 2420 aka the Twinkling Comet Cluster, 30x30s:
Jellyfish Neb, 40x30s:
You can just see the edge of it with some stretching!
More apparent with overstretch but - yuk!
I'm new to astronomy, I got my first telescope in November (StarMax 90mm f/13), I was really happy with the view of the moon and double stars, but disappointed I could see but barely make out nebula (initially the ring nebula). I also tried to take a photo of the moon with my phone but trying to get a stable shot was too difficult, even with a basic smartphone adapter.
I did a bit of research, found about about Video Astronomy/Electronically Assisted Astronomy (EAA) and decided I needed a better mount and took the opportunity to get a faster telescope (StarTravel 102 f5/). I really like the Sky-Watcher -102 AZ GTe with the ZWO ASI 224MC. I've only used it for 4 nights as there is so much cloud about but it's allowed me to take images of things my eyeball wouldn't see. Although my setup is below the minimum specification most would consider for imaging and entry level for visual observations I think I've found a setup that seems to work for me. I like that with SharpCap I can get instant results and the day after when it's back to cloudy I can get a bit more out of the images with Deep Sky Stacker and Gimp. I have tried looking through the eyepiece at the Pleiades, that was a pleasure as well. I can see how observing with a big Dobsonian and amazing eyepieces would be great, but many objects seem better with a camera than eyeballs. The Horsehead nebula wasn't found until astrophotography came into being.
The photo above was taken on my first night with the setup. The January 2019 issue of Sky at Night Magazine has a review of the Sky-Watcher StarTravel-102 AZ GTe and they give it 4.5 / 5. Combining it with an Explore Scientific UHC filter seems to reduce most of the chromatic aberration and increases contrast relative to the stars, and light pollution.
Video Astronomy/EAA seems to offer a great window into both the visual and imaging worlds of astronomy. As First Light Optics say "Your first telescope is arguably the most important because if the views do not amaze and delight, your interest in astronomy will crash and burn on the runway!" I understand cost could be an issue, but if the beginner had a suitable camera Video Astronomy could be as accessible as a Go-To visual setup, and seems more likely to amaze (especially in the skies of a typical house).
My question is why is video astronomy not the first suggestion for beginners interested in both visual and imaging?