RobW

With the weather of late ruling out much imaging I decided do some DIY organising instead:

https://www.cloudynights.com/gallery/album/25908-storage/

My office feels spacious again now the scopes aren't all up on mounts taking up half the floor space. The RC8 is still mounted. Cupboard space wasn't quite enough, and it's tail heavy which I wasn't totally sure a wooden shelf mounted clamp would take.

So sad to hear - David and I swapped a few emails about custom Dobs, and I very much had the idea of commissioning one from him some day. Came across as a thoroughly knowledgable and professional guy, and reviews and comments online suggested his scopes were the very best. May he RIP.

Lovely concept - not convinced on the $4k price tag though. If you don't have mounts and existing gear, it is all-in-one. If you have some existing gear, a RASA 8 seems a better proposition. Different strokes I guess. Maybe their target market is people wanting more than an S50, but still wanting simplicity with everything in one bundle.

This thread was super helpful, many thanks for this.

My version came out very similar - slight difference in the syntax mount and managed so far to use a standard 280mm belt:

https://www.cloudynights.com/gallery/album/24645-skymax-180/

Useful - thanks. The main thing for me is f/3.9 - I'm considering moving to a faster widefield scope. So the decision is 290mm FL @ f/3.9 or 350mm FL @ f3.9, since I'd be putting the reducer on either. There's probably a slight benefit of 90mm vs 72mm primary objective ITO resolving power, but that's not so much a factor in my thought process since we're talking widefield here anyway. FWIW - I did contemplate the Sharpstar 13028HNT f/2.8, but my existing filters could be problematic. On paper they're only rated to about f/3.6.

Also interested in thoughts with the reducer - especially pixel scale and whether it's too much undersampled on the 2600MC. Liking the idea of a 290/f3.9 very much - might consider pairing it to a asi294mm pro in bin1 mode for a somewhat better pixel scale match. Alternative would be the FRA500 with reducer, which sits at 350/f3.9

If you're a DIYer and don't mind tinkering (and possibly voiding your warranty) there's some useful tips on the internals of the SA Gti on Cloudy Nights, including how to adjust for RA backlash, which mine was gradually developing. 10 minute fix (5 of which was gently warming, removing and relocating the sticker which covers the adjustment hole). And no backlash. More info on the CN thread (including much more major work on regreasing and adjusting DEC, which I have not needed yet)

2 hours ago, vlaiv said:

Not sure if I can recommend any particular book / source that contains all the information.

I picked up things and pieced them together from variety of sources.

Often recommended is "Making every photon count", but I'm not sure how much it goes into technical detail. In any case, if you have any questions, I'd be happy to help.

Awesome - cheers. Loving this hobby. So much to learn!

On 26/07/2022 at 15:38, vlaiv said:

Yes, sorry, my bad

All correct except one thing - bin x3 will give you x3 improvement in SNR - not x2 which equates to x9 imaging time and not x4.

SNR improvement is related to imaging time by square root function, so x4 imaging time (or x4 number of subs) - gives you x2 SNR improvement, while x9 imaging time gives you x3 SNR improvement.

Since you are binning x3 (joining 9 pixels - which is equal to stacking x9 subs or imaging for x9 longer) - you get only x3 improvement in SNR - or rather, SNR improvement is equal to bin factor.

I know this fear exists with people - but that is just because people don't fully understand blur / resolution part of astronomical imaging. Resolution is not there to begin with.

If bin x3 is proper sampling and you wonder what you've lost over having 6000x4000 instead of 2000x1333 - answer is noting. If you want to have 6000x4000 image for say printing purposes or whatever - just take 2000x1333 image and upscale it to 6000x4000. Result will be the same as if you've shot 6000x4000 under original conditions.

 

This has been a very informative thread to read thanks!. Although I confess, as a newcomer. some aspects go over my head a bit at this stage. Any suggestions on good reading/research links or other sources so I can get a deeper understanding? Very keen to get a good grounding on fundamentals before I add to my existing scopes or cameras.

Just now, Tomatobro said:

I had that problem!

I made a short extension piece to go between the mount and the tripod to give the camera clearance. The skywatcher extension tube was out of stock.

 

Yeah - it's not actually hitting, so I'm OK for now. I'm considering an HEQ5 anyway, and the Az GTi does lesser duties on my other scope, so I may just live with it for now.

11 hours ago, PeterKom said:

Dear Adam,

What connection for guiding do you use USB or ST-4?

I have problems with the new GTI mount and PHD 2. I can normaly connect the mount with just the USB cable but after calibration is complete I get following error messeges:

"ASCOM driver failed checking IsPulseGuiding. See debug log for more information."
"Pulseguide command to mount has failed - guiding is likely to be ineffective"
"ASCOM driver failed checking for slewing, see debug log for more information."

Otherwise SynScan app works fine. Connection to mount works, alignment procedure works, connection to APT works, GoTo function in APT and Plate solving in APT Pointcraft works fine....

Tried to replace USB cable of the mount but problems are still there.

Mount is 3 weeks old.
Motor board version is 3.37.0C
I see online there is a Firmware: Star Adventurer GTi GOTO mount, version 3.44.
Maybe check this out?

For any suggestions i would be thankful!

CS Peter

I'm also on a straight USB connection from mount to PC (an old Intel NUC box). Couldn't see any benefit of ST-4 even though I have the cables, so I went with a simple/direct USB connection. I'm using the fairly standard NINA/PHD2 combo for software. It did take a couple of minutes after installing the ASCOM platform and drivers to figure which COM port it was using (COM3 in my case) and configure that into SynScan. If all else works, have you checked/changed the normal Altitude limit in SynScan - I got caught by that on Andromeda the other everning, which was above the 75 degrees they set by default in SynScan for the mount. I just whacked that up to 90 and all was OK (apart from shaving my tripod leg!)

One thing I noticed last night on the new version is that if I'm connected by USB to my PC I don't seem to be able to connect using WiFi from my phone in parallel. I'm sure I've done that in the past, so maybe it got blocked in this new release. WiFi from phone works fine if the mount is not connected to anything else. It's no biggie, but my PC is sometimes a distance from the mount so it was kind handy for a quick slew to target to save trudging back. Bluetooth is also listed but I couldn't get it to work on Android - I doubt it's something I'd use much anyway, my NUC PC card doesn't have working BT at present anyway (long story!). Those aside, 3.44 seems to be working fine.

Just spotted on Cloudy Nights, that SW have release a new version 3.42 f/ware which is listed on ZWO forums (to fix some issues with ASIair I belive), but the link is only currently on the ZWO site and not the SW site.

https://bbs.astronomy-imaging-camera.com/d/15229-asiair-star-adventurer-gti-problems/18

21 hours ago, SirLancelot4711 said:

By the way, update on this: I did eventually get a replacement. Long cloudy spell prevented me from properly playing around with it earlier but I did so the last few days and wanted to check a few things with you guys (going from low to high in terms of how concerned I am about them).

1. After polar alignment, when I used the GOTO function on the first SA GTI to align to my first star, it generally went more or less into the right position and I only had to finetune, which was great. This one however goes completely off and I have to move it significantly to put into the right direction. Once the first star is aligned, the rest works. Was I just lucky with the first few times and is it typical that the first alignment is totally off?
2. After doing a 3 star alignment, I tried to focus on Andromeda, but the app told me it's out of reach, despite being right above me. Has anyone experienced this? It did find other stars correctly so I would have presumed that my alignment was correct. Location and time were also correctly set.

Did you experience any of the above and have any advice?

On point 1 - the accuracy of your first star you go to will in part be how good your PA was, but also the accuracy of your home position. I've been battling with this. The GTi doesn't help much with manually getting a good home position because it has no degree scales on RA or DEC. Actually, I need to check that properly - I realise the polar scope has a scale that I may not be properly using for one of those! There's no external scales to use with levels though. Setup for visual with a wide FOV eyepiece, it's no big deal, but it's painful for a narrow image sensor FOV. It's something I need to work on next time out. Possibly your 2i was less of an issue because you only had one moving axis which could be slightly mis-aligned when in home position. Once you've done your 1,2, or 3 star alignment none of this matters - the GOTO caters for any mis-alignment of home. But that doesn't help with getting that first star alignment close enough to be in FOV. BTW - I'm a total beginner, so I could be missing something obvious!

As for your (2) I'm too new to advise - but I do recall seeing some configured limits on the mount DEC that may be worth checking out. Possibly also that a mis-aligned home could mean the GOTO is adjusting too much for the DEC axis being too high (or low) and hitting the mechanical limits.

1 hour ago, Adam J said:

USB is much more reliable, i simply cant imagine using the WIFI connection myself not reliable enough for my taste and with no external antenna on the SA GTI the range is very limited. 

Adam 

Thanks. Cable is on way today so I'll start out that way.

Another Newbie Q - are there any significant benefits/drawbacks of using EQMOD over USB vs WiFi for a PHD2 connection to the SA Gti? Reason being, if I use EQMOD it keeps my PC WiFi free for remote desktop connection and saves me running an Ethernet cable into the garden. My worry about EQMOD is if a high frame rate camera were in use, could this saturate the USB3 bus and result in EQMOD having issues communicating with the mount? I realise that high frame rates would likely only be the case on planetary imaging, and in that case maybe it's less of an issue. I'd probably be using FireCapture with a single camera then anyway rather than a separate guide camera.

On 28/10/2022 at 23:39, irose said:

Thanks StevieDvd.

So the alignment process (without guiding) should be:

1. Polar align as accurately as possible using the Azimuth and Altitude control knobs and finderscope

2. Use the SynScan App , 3 star alignment and movement controls to centre each star

Ian

I'm also a beginner - but I think there is also an extra possible step. The polar align in (1) can be "refined" with the SynScan App - in my version it's listed as "Polar Alignment" next to the "Polar Scope" function. My understanding is that this is in addition to 1+2 above - you do those first, then this does an extra/final star alignment based check with an "adjustment" using the Alt & Az controls to correct for minor polar scope alignment miscalculation. I spotted this being explained in one of the SA Gti review/intro videos. Honestly, for me results were mixed - my polar scope align was more accurate. But I only just got myself a crosshair eyepiece to help with accuracy centreing, so I need to retry now I have that. For imaging work, I'll likely just use plate solving in SharpCap or some other tool after getting a reasonably close PA using the polar scope.

8 hours ago, licho52 said:

Just get a HEQ5, the difference is enormous, even for a 400mm, which is well outside of gti's capabilities in my opinion.

Yep - if you have the budget, the HEQ5 is a no brainer. But if you want to start small, there are a few examples of guys using Askar FRA400s and WO ZS 73s though on GTis or other 5kg payload mounts and able to get 5min subs. It's a stretch, and you're gonna need to gain some real experience to make it work (which for me is much of the appeal). But it can be done if you keep your imaging train lightweight. Personally, for me, I know I'm gonna need a much bigger mount down the line - and the HEQ5 wouldn't cut it then anyway. By then i'll be looking at something like a Pegasus HWM to give me the capacity for an 11" SCT. So I'm happy with the SA Gti as a starter mount to learn on, and also use with a high quality lightweight ED refractor rig as the next stage. My tripod underneath is already sized to 40 or 50kg, so that part I know is future proofed (and also the only part that is vaguely affordable in all of this!)

16 hours ago, John Wick said:

Slightly off topic, but the Gti was on my purchase list, but i happened across videos about the HEQ5 Pro, i know its more expensive and at this time i will shut be shooting with my 6D and in the future largest lens purchase of maybe 400mm. Would i be better to go with Gti, given my short /mid term goals, or spend more while i can and get the HEQ5?

The HEQ5 is more future proof - but if you have no immediate need to go above 400mm, it's more expense than you need right now. FWIW, I'm planning on upgrading to a 72ED or maybe even one of the very light 80EDs as a full imaging rig with my Gti. It's a stretch to keep that under the 5Kg payload, but I believe it can be done (e.g. using a l/weight 32mm guide). My longer term plans also include either a 14" Dob or the largest Aplanatic Schmidt  I can lug around (poss the EdgeHD 1100). The latter obv needs a bigger mount, but quite likely I'd be running both at the same time anyway, so it's not really a duplication to have 2 mounts. That part is all ways down the road though - I haven't spent enough time outdoors or gained enough experience to know which way my interests will lead. If it's more on the visual, the big dob is a no brainer.

5 hours ago, RobW said:

You guys are all on way more advanced rigs than me (just starting out), so I doubt many have tried the built in SNAP/camera control port. But interested in experiences for anyone that has.

 

Answering my own Q here. It seems the "screen timeout" is the fatal trigger (on Android 11 at least). So not only does the SynScan Phone App need to be continually present for the SA Gti Camera Control, the screen has to be permanently on - which is going to be a battery killer. So it looks like I'll be using the Lumix S5, or grabbing a cheapo intervalometer if I continue to tinker with the GF1.

I'm really hoping the tracking does not stop if the SynScan Phone App is disconnected. Haven't read a definitive report on it, but I suspect it does keep running ok without the phone present.

You guys are all on way more advanced rigs than me (just starting out), so I doubt many have tried the built in SNAP/camera control port. But interested in experiences for anyone that has. I was getting very wonky timings - often longer or shorter than requested. Need to do some more tests, but I'm wondering if it's the Phone App playing up. I have set it not to be unloaded/stopped when in background mode. But realised after the fact I had a minor phone battery saver on which may have got in the way. I'm actually not clear yet if the app is doing real time control or sending the intervals to the SA Gti - I suspect  the former, given that it seems to also play up if I walk out of range with the phone.

So far though - after a couple of nights visuals and tinkering and one night attempting imaging, I'm really enjoying the mount. My experience is way too low to know if I'm getting backlash or other issues, but that'll come in time I'm sure. I do find the App based PA a bit all over the place, as I saw mentioned. I may just stick to my initial polar scope PA, which seems to get me pretty close. If anything, the App attempts seem to wander off from this rather than getting closer, but that could be me!

For info: I'm using a very old Lumix GF1 and 135mm/f2.5 lens combo (effective 270mm on the crop sensor) - just as a way to test the basics of my PA, focusing, exposure etc. I'll swap it out for my Lumix S5 soon on my Startravel 102T. The S5 has it's own intervalometer - so this'll be a short lived issue. But I'm waiting on the longer dovetail to balance the rig with that.  And yes, I know I'm going to get bad CA on the 102T with it not having ED glass, but I can live with that for now as I learn all the other stuff. I'm planning to add a 72ED sometime early next year once my skills will live up to it!