Avocette

The idea of jogging probably requires using the Crayford accessory - there is a lot of backlash in the Mak primary mirror focus control so I generally approach the point of focus from one direction only.

I appreciate that there are some planetary imagers who metaphorically throw their hands up in horror when people mention focusing their scopes with a Bahtinov mask. However, in my experience I’ve had much more success by using a mask to focus, either on a nearby star or else on one of the planet’s moons, than using the video image on my laptop screen. I’m using a SkyMax 150 with a Barlow and use the normal focusing knob manually to make adjustments. I do own an add-on Crayford focuser fitted with a SW DC electric motor drive, but using this adds significantly to the focal length of the arrangement, and the manual control motor focuser isn’t precise in use. Am I missing something here? [SkyMax 150 (effective aperture 140mm) with Barlow measured focal length 3445mm = ~f25. ASI533MC with pixel size 3.76um.]

I think the thread is rather centred on quite large sensor sizes, but if you’re really only trying to measure focal length, you don’t need a big sensor. Many astrophotography software will measure the accurate focal length of any scope/camera combination. They do this by platesolving an image. A large FoV is not necessary for this. In my case I have a mix of equipment, and for each configuration after any image is captured during polar alignment or guiding, my software immediately indicates the actual focal length of the combination. For instance my SkyMax150 with a simple visual back with a closely coupled camera measures 1922mm and when a so-called 2x Barlow is inserted the focal length measures 3445mm giving a measured Barlow ratio of 1.79x. My Sky-Watcher EvoGuide measures 253mm rather than the specified 240mm. You might consider getting hold of (or borrowing) a ASI120MM-mini which has its sensor chip very close to the face of the camera (8.5mm according to the specification). This camera would be a good investment if you ever do get into imaging and in particular guiding!

I run my equipment in various places in the garden to optimise clear, obstruction-free views, but all slightly further from the house (up to perhaps 30 feet maximum). When setting up, carrying out polar alignment and monitoring the first few captures I am close to the mount with the laptop on a small garden table. Afterwards indoors, I have the laptop near a patio door so the WiFi is only penetrating through glass. With the RPi4 and Astroberry software package I force the WiFi hotspot to use the 5GHz WiFi band since there is evidence that the 2.4 GHz band interferes with the use of USB3.0. My RPi4 is in an aluminium ‘flirc’ case, mounted so that the plastic bottom face is away from mount metalwork. This works very well for me - I even run two Astroberry rigs from the one laptop by setting up two different 5GHz hotspot SSIDs (AstroberryBlue and AstroberryRed).

At any time of the year your laptop would be susceptible to dew, possibly more than to frost…. I use a plastic storage box on its side (rather than a cardboard box) to enclose the laptop which is a 2019 model which runs on its lithium battery for around 8 hours. I run Astroberry on a Raspberry Pi at the mount and link in with the laptop with WiFi to control it, and when I go inside to warm up I carry the laptop and storage box with me, leaving Astroberry to continue without interruption.

I pimped my Dob some years ago - if you haven’t seen this thread, why not take a look!

Some distance away from Tenerife I was busy capturing Jupiter and these three Galilean moons at the same time. Here is a GIF of the transit and occultation event… SkyMax 150 Pro Maksutov-Cassegrain operating with a 2x ED Barlow with shortened spacer at focal length of 2762mm (f19.7). ASI533MC ROI 300x300 pixels. FireCapture 2.7.10, AutoStakkert!3 & Registax 6. The twenty or so still images which make up this GIF were 25% stacks of 10000 frames from one minute of captures every second minute. So the original 20GB of captured files were squashed into a 600kB GIF - with some inevitable quality loss of course.

Yes - I was probably too quick and used the same Rx6 parameters.

Thanks @vlaiv and @Sinemetu63 for the ongoing discussions! I have reprocessed completely my earlier image to avoid the 1.5x drizzle, but I feel I lost a lot of important detail that was evident in the earlier version. I had understood that x1.5 drizzle processing in AS!3 was not just rescaling.

Here is one of my Jupiter captures from 6 October. This is the 1.5x drizzled output from AS!3 via Registax 6.

@vlaiv I am also using a Mak 150 with a 2” ED Barlow, although mine is nominally 2x. From platesolving an image in Cygnus with plenty of stars, the focal length measures 3445mm. This gives an 11 arcminutes square FOV for my 11mm square ASI533MC with 3.76μ pixels. Hence sampling at 11x60/3008 or 0.22 arcsecs/pixel. I have read and reread your post but am struggling somewhat to understand the detail of your analysis! Of course I would like to think that I am achieving similar results to @Sinemetu63 who coincidentally is just the other side of the Alps from me. However I have always been unsure of my telescope which I found was out of collimation when I bought it third or fourth hand, with a collimation screw loose! I attempted collimation over the years and most recently with the encouragement of posts from @Captain Scarletam starting to feel it is pretty well aligned. I have also recently started to realise just how influential the seeing is to the results I obtain. I would be happy to post some of my recent results if you could be interested to apply your analysis tools?

Hi - perhaps the easiest way is to download Astroberry (astroberry.io). This is a great compilation prepared by @RadekK and including FireCapture 2.7.10 ported specially for Raspberry Pi. The present Astroberry image for downloading was compiled a year ago, but since then Radek has set up a repository with regular updates, so you will need to carry out an update/upgrade which will make a lot of changes. I’m assuming that since you own an RPi4 (gold dust due to supply shortages) you know a bit about burning an image onto a microSD card or SSD and Raspberry Pi OS commands.

I am very impressed that you are within 0.1° of 180° which as you suggest is rotated one half turn. I usually achieve within a couple of degrees of 90° or 0° depending on the portrait or landscape aspect I am using to frame my target (with an APS-C 3:2 aspect ratio ASI2600). I have no personal knowledge of Astrometrica, just of astronometry.net and Ekos.

I've just checked my RJ12 EQDIRECT adapter and found it contains a Prolific chip. But there again so does my AZ/EQ-5 internally hidden behind the USB socket and I have no problem making connection with it from Indi on the RPi.

That's exactly why I was asking for advice - the SourceForge webpage has such warnings but where does the 12V risk come from? The RJ45 EQDIRECT cable for the AZGTi has only three connections made Gnd, RXD, and TXD, although I suppose there is a 12V line in the AZGTi RJ45 socket for use in powering a SynScan handset.

I have a HitecAstro EQDIRECT cable bought years ago for use with an EQ-5 Pro mount which was subsequently sold. I now have an AZGTi which I want to drive by cable. I thought of modifying the HitecAstro cable I have by either replacing the RJ45 (8 pin) connector with an RJ12 (6 pin) or alternatively making a converter cable using an RJ45 socket to RJ45 socket Ethernet extender and a short RJ45 to RJ12 cable. Has anyone already done this, and any advice for me please? I have read the EQDIRECT information page on SourceForge, although it has left me somewhat confused…..

Hi and welcome to SGL! To start the process of giving you some ideas it would be helpful to know what sort of mount/tripod you’re using with it, and what eyepieces you have. And most importantly, what the sky darkness is where you will be using it. For instance I have a SkyMax 127 with similar properties to yours. I use it on a Alt/Azimuth GoTo mount called an AZGTi. I have a number of eyepieces, and I have tried taking photos of the Moon through it. Where I live is suburban with bright street lamps shining into my garden so with my eyepieces I concentrate on bright objects, double stars, star clusters, the Moon and the planets. I have successfully photographed the DSO (deep sky object) ‘Messier 27 - the dumbbell nebula’ which is a relatively bright object. With my eye I could only just persuade myself that I could see a faint grey shape, but with the electronic ‘eye’ of my astronomy camera and around 100 x 30 seconds images, I was able to make this image:

Which autofocus software are you running? With your RPi4 I guessed you might be using Astroberry or StellarMate and hence Ekos. The latest version of KStars (3.6.0) (in StellarMate but not yet updated in Astroberry) is said to be yielding better results with a new version single pass linear process. The single pass establishes the V curve, finds the HFR minimum, the focuser is then displaced back to the other side of the curve, and starting from the original position moves again in the measurement direction to the step number where the minimum was found. Hence errors due to gearbox backlash should be eliminated. I write this waiting excitedly for Astroberry to be updated, having just replaced two SW DC motor focusers with ZWO EAFs!

I use the ASI533MC, which I bought in spring 2020, on my ED80 with FR/FF at 510mm. They work very well together with an FoV of 1.25° x 1.25°. When I subsequently bought a 61ED refractor, with its FR/FF at 275mm, for more widefield shots on my second mount, I used my astromodified EOS550D with it for a year. But the wonderful performance of the ASI533MC made me justify to myself buying an ASI2600MC. I began by using it with the 61ED, and the resulting FoV around 5° x 3.25° like with the DSLR, is such a good match, that I have never swapped it over to the ED80.

I use SynScan Pro with SkySafari 7 Pro on my iPad. Connect to AZGTi WiFi hotspot, open SkySafari and adjust Telescope Preset setting to AZGTi. Click to connect telescope, and SynScan Pro will automatically open. If you’re using standard left hand AZ motor firmware you’ll be returned directly to SkySafari with the scope view FoV drawn on the sky. With right hand firmware you will need to select appropriate operational mode.

Could you post a photo of the misaligned finder mount base? I would have thought you could do something to realign the base without replacing the whole focuser.

It’s certainly true that Raspberry Pi 4s are in short supply at the present. I’ve been running two Astroberrys on 4GB versions I bought just after they were released in 2019. With your SkyMax127, you are unlikely to be tackling long periods of capture, and at this time of year, remote working is not so essential. Working locally close to the mount using SharpCap or other Windows software on a laptop would be an option, although it’s always convenient to be wirelessly connected via an RPi or other device. While waiting for the planets to arrive in the evening skies, I have been using a my SkyMax127 guided on an AZ-EQ5, with short (15 seconds) exposures to improve the guiding statistics in blustery conditions. Here’s the result of 30 minutes of captures (120 subframes) processed only in AstroPixelProcessor. The KStars/Ekos/Indi package on Astroberry is now (v3.5.9) pretty stable. I used it to capture Lights, Darks, Flats and (automatically) matching DarkFlats.

I think your calculator got it right! My own thinking was a bit loose and very optimist!

Lovely image (and especially from such a short nine minutes of total integration time)! Just curious about the 5 second exposures. I have been shooting 15 and 30 seconds recently because of blustery conditions, but otherwise tend to go for 120 to 300 seconds range, guided, with my f4.5 and f6.5 refractor/reducer combinations. 5 seconds at f2 equates to 11.25 secs and 16.25 secs at f4.5 and f6.5 respectively, and 8.75 minutes at f2 to 19.7 minutes at f4.5 or 28.5 mins at f6.5, all of which seems quite unexceptional.

In SE Northumberland you are probably in an area with Bortle 7 levels of light pollution. At Kielder you would be in Bortle 3 (there is a good reference to Bortle on Wikipedia). In Bortle 7, visual observing will require quite a bit of preparation to make sure you can get your eyes accustomed to the dark, and keep them so during a session. Dark screening panels and an eyepatch may help. I live with Bortle 5 conditions and several yellow streetlights that play directly into the garden where I do my astronomy. I was out last night observing the moon, but didn’t try other objects except for aligning my mount on bright stars. You may be able to drive to a darker sky area, not too far away. I can reach Bortle 4 skies in half an hour.