KP82

On 24/12/2023 at 08:50, Ags said:

Not sure on this. Doesn't the EQ5 also have 144 RA teeth? The EQM-35 has more.

Not sure how much of an issue the servo motors are. The AVX also uses servos and seems well-respected.

Last time I read the specs of the EQ5 Pro the RA teeth was 180. Or maybe SW have updated the info to 144 and the previous specs was wrong.

Servo is fine. Even the Losmandy G11 uses servo motors albeit higher quality ones I suppose. But for a budget mount I'd prefer stepper over servo tbh.

Looks like a mechanically downgraded EQ5 (based on its RA/DEC teeth number & servo motor spec) with a dual position counterweight bar and built-in wifi. Honestly ppl are better off with the regular EQ5 + the new shorter extension pier or HEQ5 if higher payload required.

There was going to be one on the 18th Mar at Sacrewell Farm, but it got cancelled.

There will be another one hosted by Burghley House between 22nd and 23rd Mar: https://burghley.co.uk/events/stargazing-evenings-at-burghley-house-artemis-footsteps-on-the-moon-2. But the tickets have been sold out.

In your case larger apertures alone would offer limited improvement for visual observation of DSOs. You will need some visual narrowband filters (UHC or better OIII). Your current mak makes getting larger exit pupil difficult but you need a decent size exit pupil for the filters to work at their best. So a fast 10" f/5 dob will be a good option. However these filters can only help you with certain type of targets mainly nebulae. Galaxies will be difficult to see.

Star hopping with a dob should be no different from your Skymax 127 assuming it's also mounted on an Alt-AZ.

Have you updated the mount firmware to the latest version? The earlier versions had 3 modes (WiFi w/ ExploreStar app, WiFi ASCOM & Serial) and if the mount was set to the mode other than WiFi w/ ExploreStar, you wouldn't be able to control it with the app. If that's the case, you will need to connect to the mount via USB and change the mode (or better update the firmware) with the ES desktop software.

More info can be found here: https://espmc-eight.groups.io/g/MAIN/topics

The Powerbox has a built-in FTDI chip and connects to the PC in a similar way to a mount. You will need to find the correct COM port in the device manager before trying to control it with the software.

If I were to get a Tak, the primary objective wouldn't be for its superior optical quality (the difference is only marginal compared to the other 4" f/7 fpl53 like others have said) but its portability. If you were thinking of mounting a 4" apo on the AZ mini, the FC100DC would probably be the only valid option that's currently available.

One of the reasons you get so many suggestions on Tak in any refractor discussions is that it IS the only premium APO brand which you can easily buy off the shelf (relatively speaking). The others such as AP, TEC, LZOS and CFF are basically either locked behind a long waiting list/time or obtainable by luck through used markets.

6 hours ago, AstroKeith said:

I'm using a 6 deg fov (cheapo 50mm cctv lens on an ASI120MM-S). I was initially surprised to find that blind solving (ie no RA & Dec seed) was as fast as seeded. Bracketing the image scale by +/- 5% was critical.

Also binning x2 helped on speed and reliability. I also turn off plots etc.

Looking at the index files needed for such a large field of view, I can see they are quite small, and after the first solve, the PI OS automatically keeps them in ram.

The 6deg fov is perfect for visual use. It produces a solve accuracy of about 20 arc seconds which is more than good enough. Plus it means I dont need to physically align it with my main scope. I have a software routine than automatically measures the finder to main scope offset and save it for the session.

As I have my own drive design, I was able to code in the option of an automatic plate-solve at the end of each 'goto', which then triggers any adjustment needed (aka 'goto++')

IMX477 with 180mm FL produces 2deg x 1.5deg fov. So the index files required are substantially bigger. However with the correct details passed to the astrometry.net solver it is still very fast. The 1.55um pixel size produces a resolution of 1.78 arcsec/px which is a little too much but the Pi HQ camera is OSC so binning doesn't work unfortunately.

The function of measuring the offset automatically sounds really neat. I had to write a script to produce a live feed of the camera with a crosshair overlay in the centre and display it on a webpage for alignment with the main scope.

2 hours ago, AstroKeith said:

Stellarsolver uses astrometry.net, so in theory should work. 

However, astrometry.net can require a significant number of arguments to accompany a solve request. Many are optional, but many are key to successful solves. Image scale limits for instance are critical.

Stellarsolver may be making shortcuts when it calls astrometry.net. Most worrying for me is that astrometry.net normally refers to a astrometry.cfg file to find its default settings. Stellarsolver doesnt use this and buries the settings in its main program.

After some considerable experimentation I have found a set of arguments that enables astrometry.net to solve my images with about 99% success, in about two seconds, on a raspberry pi.

I believe you're right. Stellarsolver could be making too many assumptions on data in its shortcut such as fov and resolution. 

Anyway Ekos plate solves with astrometry.net very quickly (2 - 3 secs) and accurately, so I can't be bothered to fix the stellarsolver on my RPi.

On 10/01/2023 at 17:22, Elp said:

Have you downloaded all the astap databases? Otherwise it needs an internet connection to plate solve to online data.

The standard H17 database does cover the fov of an IMX477 with 180mm focal length (SW 50mm finder). It could be at its limit which may explain why astap was unreliable (I might give the H18 database a try). astrometry.net with the correct databases downloaded have been working beautifully.

On 10/01/2023 at 21:24, skybadger said:

Thanks KP82. 

I deleted astrometry.net from my Win pc because it was so slow compared to astap and then found that astap had a dependency on it locally. I use it for between 1800mm and 1200mm focal lengths.

What are you using to pole align that can use the rpi pictures ?

 

The astrometry.net database files are huge for smaller fovs. Maybe that's why it was slow on your PC assuming it was a fairly old PC you were using?

The PA module in Ekos.

On 11/01/2023 at 09:00, AstroMuni said:

It may have something to do with sensor size. I have trouble using ASTAP & Stellarsolver in some areas of the sky using the ASI224, but thats both on RPi & Linux Mint.

The internal stellarsolver presumably shares the same database with astrometry.net. If astrometry.net can solve the pictures taken by IMX477 + 180mm FL, I don't understand why stellarsolver can't.

45 minutes ago, AstroMuni said:

Is there a reason you are not using the internal Stellar solver?

It always fails to solve no matter what settings I change to. Could be something to do with how Kstars/Ekos are compiled in astroberry or how the internal solver handles the FITS data from the RPi HQ camera.

I don't have this issue when using kstars downloaded from the official ubuntu INDI repo "mutlaqja/ppa" on my NUC with QHY or ZWO cameras when imaging.

3 hours ago, skybadger said:

Can we hear more ? 

Like, what app is doing the solving, how much it impacts the rpi, what the sensitivity is like, why you use a button , the process to tell astroberry where the solution is currently pointing, how you manage or check for differential flexure, etc. 

There's a couple of solutions for this ( auto alignment Vs guiding)  and auto alignment could be continuous vs guiding which occurs during imaging.

My perfect solution has an auto alignment scope and oag guider. 

This setup is strictly for visual only. When imaging I use a more traditional guiding setup (Evoguide 50ED + 120MM) connected to a NUC running ubuntu.

For visual the RPi uses Kstars/Ekos for plate solving (astrometry.net which I find to be more reliable than astap). It's connected to my phone running SkySafari Pro. Because SkySafari does not provide a way to trigger the plate solve nor do I want to switch between it and VNC (cumbersome plus it ruins my dark adaptation), I use the button. Once pressed Ekos will plate solve and then auto align the mount. And since the finder is already aligned with the main scope, whatever it points to will also appear in the eyepiece of the main scope. The correction process gets displayed on the SkySafari (very useful).

Differential flexure is not an issue at all here because there is no continuous exposure involved. The RPi HQ camera (IMX477) is pretty decent for the task. The gain is set to 4.0 and exposure to 2.0 sec in Ekos. So far this seems to be optimal. The combo is also used for precise PA. It takes less than 5 mins (in VNC) and improves the RA tracking significantly.

RPi4B (astroberry), RPi HQ camera mounted to a 50mm SW finder and a USB power pack are all you need. This is exactly what I've been using for nearly 2 years. I wrote a couple of python scripts to allow plate-solving with a simple button press and alignment between the finder and the main scope.

ED80 + HEQ5 + 533MC Pro for hassle free (relatively speaking) start of AP

or

130PDS + HEQ5 + 294MC Pro if you don't mind learning collimation of a newt

Both are for wide field DSO imaging. Like others have said the most important part is the mount. You may also want to grab a 30 - 50mm guidescope with a 120MM for guiding.

I've got the WO short handle on my 80EDT. The end M6 holes are exactly 120mm apart.

IMHO for any short (< f/8) sub 4 inch scopes, there aren't any benefit with losmandy dovetails compared to vixen.

What you're looking for has already been achieved by scopes with folded optics (ie. cassegrain) that offer much better image quality than your proposed barlow solution. The weight of cassegrains depend on the size of their mirrors, but they are already as compact as possible compared to newts or refractors with an equivalent aperture.

The aforementioned budget newt (aka bird jones) produces poor views mainly because of its spherical mirror. But even if it had a parabolic one, it would be extremely sensitive to collimation errors and adding a barlow wouldn't change anything.

Another vote for mini-PC.

Personally I don't like brand lock-in. An used Intel NUC or Pi4 could do pretty much everything that ASIAIR offers at a much lower cost. Yes the dedicated ASI app is more elegant than using RDP or VNC on a tablet, but imho not worth the extra cost especially if you're like me who prefer using a PC and its larger screen instead to remotely access the NUC/Pi.

I moved from BYEOS to NINA and then also Kstars/Ekos now. Yes there was a learning curve when switching to a different imaging software, but nothing that couldn't be sorted out after a couple of nights out.

I've got both the TS 0.79x reducer and the riccardi M63. With the TS the corners always show a bit of curvature on APS-C no matter what spacing I used until I replaced my DSLR with an QHY163 (smaller M4/3).

The riccardi is a lot better in terms of field correction, tight stars and flat across the entire field of APS-C. My sample is an older version I bought used here. The surface of its internal barrel is matte black. The later version seems to suffer from stray reflection due to its shiny barrel surface. I can't remember where I saw the thread (could be on CN) in which a member posted a comparison between the two versions. The shiny internal surface could be clearly seen in the pictures.

Got patches of cloud in the sky but fortunately none was obscuring the Sun. Took this with the phone.

If you must have a quadruplet (or even more lens elements) flat-field refractor larger than 80mm for imaging so that you don't have to deal with separate flatteners, your options will be quite limited.

Askar 107PHQ, 130PHQ
Sharpstar Z4 (sextuplet, new release, no review yet)
TS-Optics APO100Q, 121SDQ (made by Sharpstar)
Tak FSQ85, FSQ106EDX4

Askar petzvals are very popular lately, so a lot of reviews/personal experiences to be shared around. Unless you're willing to increase your budget to get the Tak 106, the Askars are probably your best bet.

Excellent result with only 30min integration time. The IMX577 is so good that it makes my panasonic sensor based QHY163 like a prehistoric device.

The altair lightwave .8x FR/FF is designed for refractors between f/5.5 and f/8, so should work with GT81 theoretically. Personally I've used a generic TS .79x FR/FF with 3 different scopes (WO Megrez 90, Altair 72EDF and Altair 80EDT-R) and found it worked ok. In the extreme corners I could still see a tiny bit of elongation in the stars, but that was acceptable to me. The real pain with the non-dedicated flattener was I had to figure out the backspace by trial & error and it was different for every scope. That's why I got the riccardi with my APM 115.

As for the quality of GT81 I don't have any direct experience, but heard it's good.

10 minutes ago, Clarkey said:

There will undoubtedly be some CA at F6, but nothing that could not be removed relatively easily in processing or with an L3 filter. However, looking at the specifications again the Starfield is probably a better bet.

I do think there is a bit of an obsession with FPl-53 over FPL-51. A well made FPL-51 is likely to perform as well as 53

It's not only the blue bloat, but there is also loss of the details due to CA and SA with a fast ED doublet like the 110mm f/6.

Sampling with an IMX294 at 660mm with detail loss due to CA, SA and seeing, I believe the end result would be quite soft. As for the exact maths, you will have to ask @vlaiv for help.

On 24/07/2022 at 22:20, bosun21 said:

I was looking at this scope as well, however another £300 pounds over the Starfield 102 for visual astronomy is stretching it a little for me.

If you were going for the 115 triplet, make sure your mount can handle it as it's significantly more hefty than the 102 doublets.

There are slow-motion knobs on the AZ5, so tracking at medium to high power shouldn't be an issue. Personally this is a must have feature. However motorised mounts with their auto tracking still win here in terms of convenience.

As for low power sweeping, yes you're absolutely right. Manual sweeping is much more intuitive, fun and satisfying than fiddling around with buttons on a hand controller.