wimvb

My first astro image for the season. Last week we had a few hours of astrodarkness and clear skies, so I snapped this image of ngc 7331 and Stefan's Quintet. The atmospheric conditions were rather mediocre (guiding about 1", and the autofocus routine also reported high HFR values). I have tilt in my focuser, but as I have a FeatherTouch incoming, I won't remedy that now. This image is only 10 x 300 s G and B, and 15 x 300 s R, with a synthetic Luminance. Gear: SkyWatcher 190MN on an AZ-EQ6 mount, ZWO ASI294MM camera at -10 C and 0 gain

Is there any particular reason you got photometric filters? These weren't designed for LRGB imaging, but rather to do photometry. Also, in stead of using a yellow filter for L, try combining data from the other filters to create a synthetic luminance. Specifically, the Exoplanet filter is blue blocking, so will dim any blue areas in your RGB image if you use it as luminance.

There is no such thing as a free lunch, not even in AP, I guess. I was aware of the need for accurate modeling. But the point is moot; I see no future where I could, or even would, invest in such a mount for my backyard observatory.

I Aye!

Worse: Hwæt. We Gardena in geardagum, þeodcyninga, þrym gefrunon, hu ða æþelingas ellen fremedon. Oft Scyld Scefing sceaþena þreatum, monegum mægþum, meodosetla ofteah, egsode eorlas. Syððan ærest wearð feasceaft funden, he þæs frofre gebad, weox under wolcnum, weorðmyndum þah, oðþæt him æghwylc þara ymbsittendra ofer hronrade hyran scolde, gomban gyldan. þæt wæs god cyning.

To paraphrase @Alan White "In the UK you have a flippant sense of humour, often missed by those who speak the language but not a native." In other words: you lost me there, Dave

Ouch! Fortunately the OP assumed no budgetary constraints, but I know better ways to spend that money. If I ever get interested in such a mount, I will start shopping accessories at my local gym/sports outlet.

Before I built an observatory, I converted a cheap tool shed into a roll away obsy. It worked great, but I had the space for a permanent construction with a pier.

It would need to fit in my observatory.

It depends on how comfortable you feel with leaving expensive gear unattended. If an obsy is out of reach, the what about a roll away shed? You have the possibility to install a small heater, while everything can be left on the mount. If you hang anything over the scope, you have the risk of bumping into it. I would at least remove the camera after each session.

One that won’t need guiding (10Micron, AstroPhysics, Fornax, …). One less thing that can fail.

The mount looks so much out of balance that it almost looks like you’re a permanent part of the setup. 😉

So, how do you polar align this behemoth if it's bolted down?

I've used an IKEA FLOALT LED panel in combination with several layers of white cotton fabric for years. Worked well enough. A friend uses a LED panel from Bauhaus with good results. It's mounted on the observatory wall.

Without a guide camera, no guiding. You can use a camera for only one purpose, imaging or guiding. I’ve bever heard of anyone using a dslr for guiding. My guess is that the image download time is too long.

Yes, you can. I suggest you do some practice runs with PHD2 from your home, because there is a learning curve for anything astrophotography related. Image a few bright nebulae or galaxies (ngc 7000, the North America Nebula; M31, the Andromeda galaxy), just to get yourself familiar with the software. If you want the full image acquisition suite, check out NINA for Windows, or Kstars/Ekos for Linux. The latter runs on a small single board computer, Raspberry Pi. Very portable, but some knowledge of Linux required. There is/was an image capture program specifically for Canon, called BackyardEos. But I’m not sure if that is still maintained.

At the very least you need to be able to set up a sequence of long exposures, longer than the 30 " limit of most dslrs. With what you have you can make a good start. From there on, you can choose to have software frame the object (plate solving), do autofocus, assist with polar alignment, mosaics, etc etc. There are several software packages that will let you automate most of an imaging session, both for MS windows (ASCOM based) or Linux (INDI based).

For pure visual use, I think I would prefer an AltAz mount. It’s more intuitive and keeps the eyepiece in the same position. The aluminium tripod is also a bit wobbly for 1000mm focal length. But other than that, 👍

This may help. The thickness of the secondary shouldn't be part of it. Offset is always calculated relative to the reflecting surface of the secondary. Btw Diameter_primary / Focal_length = 1/F_number edit: the exact formula for offset is in the spreadsheet. Just enter the appropriate numbers into the yellow cells. There are approximations in earlier posts of the same thread.

For that price you could get 3 x EQ6-R with on each a SW 190MN and an ASI294MM with filter set and OAG (no guide camera), and a coffee. 😄

The one with the smaller diagonal? I've read that SW made a design change in the MN, upgrading the secondary to a larger diameter. The larger mirror made the telescope better suited for AP, at the expense of slightly lower contrast. (This changes the offset with only 0.1 mm.) I reconfigured the Pi so that it will boot from the SD card, and use the SSD for root file system (including all software). Trying to get it to boot from SSD wasn't as easy as every online tutorial made me think. Not all SSD adapters are fully compatible (my SSD is a cheap internal model with a casing and SATA - USB adapter). But instead of 29 GB storage for images, I now have 220 GB, plus higher speed, and longer lasting. (SD cards aren't meant to be used as system drives.)

I've been playing with WinLens to learn more about the Maksutov design, but summer vacation put a temporary halt to that. I will probably continue with it in the autumn. Atm I'm trying to get a ssd drive to work with my Raspberry Pi. Your suspicion that SW may have used the wrong offset is interesting. I'd think they would have corrected such a fabrication miss by now. The 190MN isn't exactly a new design. But imo, SW should release their in house alignment procedures. It would make life a lot easier for all MN users. I don't think such procedures would contain any trade secrets.

Does that mean that the marking on the secondary mirror is at its physical center? I always thought it was at the optical center, hence trying to get that little circle to line up with the cheshire crosshairs.

Ok 😉

I plugged in 190MN numbers in Suyters exact formulas, and got the same value as you: 2.7 mm Here's the spreadsheet I used (LibreOffice, converted to Xcel format) Yellow fields are input Red fields are calculations Offset_calculation_190MN.xls