rotatux

I'm not a user of DSS, but it definitely has outlier rejection available. From some screenshot I found it seems "Average" is the default, so as a start try one of the two options outlined below :

Hello... what is this showing exactly ?

If I assume this is the result of stacking, then these tracks may be from hot pixels moving with sub-frame registration. Then yes dark frames and/or bias should help, but not only...

I also suspect something else : as these hot pixels move with the result of registration, they should be eliminated by the stacking algorithm rather then leaving a trace. That is, if you used the correct stacking algorithm => You should activate and use some form of outlier rejection, which is often an option in stacking programs, they are called differently so I will just cite "sigma clipping" or "winsorized sigma clipping" but there are others. If you tell which program you use, maybe others using the same will be able to complement this answer.

On 06/06/2023 at 12:50, Gasman said:

creating a negative pressure behind it to form a concave surface and maybe it could be used optically?

Certainly. As said it has already been done. AFAIK this kind of deformation gives a "chainette" curve, which is a hyperbolic-cosine, which in turn is near hyperbolic and parabolic. 

Other deformation based telescope mirrors about which I read/views in the past 40 years :

• using vacuum behind a spheric mirror to turn it to nearly parabolic
• using mechanical traction with a screw behind a spheric mirror to turn it to nearly parabolic (I think it was in old S&T)

On 19/06/2023 at 02:23, sswcharlie said:

I am unable to download the file as it shows as a single line

Yes it looks like some HTML somewhere has eaten end-of-lines. The source HTML shows the same, so no way to recover it, apart by breaking the lines yourself.

On 19/06/2023 at 02:23, sswcharlie said:

Would like to know if unipolar or bipolar was used.

Don't know what was used - TL;DR. If you want to use the stepper with ULN2003 you have no choice but to use as unipolar (4 energy + 1 ground = 5 wires).

Of course you could cut the wires, let the ground alone, and connect the coil ones to a bipolar controller, but I don't see the point (destructive mod, same stepping, double coil inductance to fight).

On 26/05/2023 at 22:21, han59 said:

These old camera lenses are no so good

Having tried a 44M-6 myself I could have predicted this result  and can tell you have to close at least 5.6 to improve a bit (far from perfect) on this lens. Its renowned swirling bokeh is due to severe astigmatism so not much can be done.

However don't ditch all old glass, as most are much better than that. e.g. a 50mm/1.7-1.8 from Asahi/Takumar, Pentacon or Minolta will be perfect or nearly from F4 on.

12 minutes ago, powerlord said:

I'll probably use a hall sensor to ensure its position stays synchronised.

Gives me another idea. ESP32 has touch sensors. You could also use capacitive pads to check alignment : I mean, 2 facing conductive pads, one on each side of the rotating parts, and the touch would trigger when the pads are aligned enough (only one side needs to be connected to a pin).

23 hours ago, vlaiv said:

That code style is not the best for what you are trying to achieve.

+1 Vlaiv is mainly right and here is why : on embedded devices the duration-based sleep is approximate, in nominal situation it's usually a minimum but in case of hardware interrupts some devices can exit the sleep prematurely and return control to your program. So usually this kind of loop will drift from its target period, so much that it will be useless for sky tracking.

Rather than turning to power consuming "active" loops, you can get the best of both worlds by using time monitoring in the loop, which is called a fixed-rate passive loop (vs your fixed-delay passive loop).

The code to use is basically the one shown by Vlaiv, completed with :

• as calculate_time_of_next_event function : time_of_next_event = time_of_next_event + target_rate_average_period (can even be a float)

• use as microsleep : sleep(time_of_next_event - current_time())

This kind of loop will automatically compensate for both early and late sleep exits on the scale of several steps, to achieve a very precise average rate (depending on the precision of your embedded device's clock).

EDIT : crossed with other answers  but nothing contradictory

Hello, nice project.

Just like a motorized barn door tracker, you need to count steps of each part of your mechanism, and join them (multiply / divide depending on input/output situation) to write an analytic equation. Parts include gears (number of teeth per full revolution) of mount and intermediate transmission, stepper motor (steps per revolution), and sky (360° / ~23h56mn).

The base equation is mainly : 1 main mount gear revolution = 1 day. Develop the left part with gear ratios, down to stepper total steps and period, then you will be able to extract the period = seconds or milliseconds in 1 day / some number of steps.

HTH

4 hours ago, Jim Smith said:

Off Centre Diffraction Spikes

I can see double spikes on some, but none clearly offset from centre ; I read this can be caused by twisted spider vanes.

Very nice already (esp. star colors around Crab Neb.), shows if needed that AP is possible with Alt-Az. I hope you will add more subs to those, they deserve to gain more depth and detail.

On 25/12/2021 at 11:38, Pitch Black Skies said:

The idea of the primary baffle is not really to mask the clips but rather the area between them, along with the clips.

I already understand the enough repeated principle of the primary baffle, But that's not what I want, because I believe  (can't re-check at the moment) to have a quality-chamfered mirror variant described by alacant. My problem is now *only* the shadows from the clips -- as I already fixed the protruding focuser ; I find the remaining (uniform) diffraction from the bevel acceptable or even nice

I'm also not very comfortable with the silicon solution to remove the clips, as I typically transport the OTA upside down in a photo suitcase.

20 hours ago, Jim Smith said:

I'm pretty sure I screwed the clips down quite tightly when I fitted the ring baffle. They were already tight. I will loosen them

Yes my first reaction seeing your shot was about pinched mirror. The clips, if you keep them, must *not* be tight but just screwed enough to secure the mirror and avoid any play and vibrations. Of course other answers (astigmastism, CC spacing) are also valid.

BTW about an aperture mask, to avoid reducing the aperture I'm thinking about masking just the clips with half-circles of cardboard or hard paper, which would be sandwiched in the head of the clips. Would it have a chance to work ?

That's because USB cable length is limited depending on standard : AFAIK 3-5m for USB2 and 2-3m for USB3, as there's a drop in voltage with length the SnR for high frequencies is too low and doesn't allow high bandwidth of USB3. Hence the behaviour you observed.

But that's only the case with dumb cables such as the one you point. With active cables you can reach longer length as the signal is repeated and stronger (at the price of power usage, and a bit of latency and bandwidth). So if you really want to try 5m with USB3 you need to buy an active cable.

Hi, I'm in a setup process for a recently bought Altair 224C on a Linux netbook. Having driver problems with the cam, so I'm not yet operational enough to be sure. Indigo seams richer (more drivers) and more polished than Indi, with a similar or mostly compatible protocol. AIN Imager looked very nice when I tried it, probably better than CCD Ciel which seems the nearest alternative.

Same problem as you for training in-house without a starry sky. Asking myself if a sky print in front of a lens would trick it 😄

23 hours ago, Gina said:

I haven't yet found what Cinnamon does that MATE doesn't.

It's all about what Cinnamon does not that all other desktop interfaces do : ability to launch some programs (e.g. Terminal) several times. I think its "activity" based design is the culprit for your experience of not launching several terms. Maybe just a setting (dunno), but I don't think it was the terminal's own fault in the first place.

BTW If you're used to Cinnamon ergonomics, you're probably going to dislike all other desktops (*me* prefers old windows+launchbar desktop style)

Yes absolutely : Unless it's under ReiserFS like mines (which becomes unsupported in some so-called-modern distros), "calamares"-based installers allow you at install time to reuse an existing partition and "mount" it at a restricted choice of directories ("/home" would be your appropriate choice).

The point is, your previous partition was mounted as root (/), so your personal files were stored at home/gina as relative path in the partition. If you mount it without change in a fresh install as /home, the full path to them would be /home/home/gina so not the expected place. Fortunately Unix has symbolic links (created by the "ln -s" command cited above) which allow to relocate files and folders in appearance without moving them physically.

An alternative reuse scheme is to mount your old partition at a completely different path such as /mnt/oldmint, then link its home folders into the new install with "ln -s /mnt/oldmint/home/* /home/". This way you don't even touch the system part of your old install.

Possibly same story for your software in /opt or /usr/local (I understand you may have some).

In every case you will have to take care that owner and group names and numeric ids of your files coincide between old and new install, or you would not be able to log in as "gina" afterwards.

18 hours ago, Gina said:

Maybe I need to create a partition in the gap and then install there.

Yes, given its volume, may be better to keep /dev/sda1 as your future /home. If you mount it without formatting, you can get your accounts back by declaring the same users names with the same numeric UIDs (and possibly GIDs), and then relinking the folders to the expected place ("ln -s /home/home/* /home/") or move them definitively once your new install tested.

BTW don't allocate the whole 66GB to a single partition, use a tighter fit  such as 10-20GB, so that you could add more of them afterwards -- and better, use LVM if you're comfortable with it (fewer distros support it nowadays). The command "du" can be a helper to find your size requirements, such as in "du -shx / /var /home" (list your mount points).

15 hours ago, Catakraken said:

the image I see when I connect it is the one I attach. I can't adjust the green circle in the circle created by the end of the focuser.

As already said a possibility is camera tilt because of the attachment screws ; Another possibility is the focuser is tilted by itself ;
For the first case, try wrapping the camera barrel with a band of paper (maybe several turns) or duck tape so that you barely need the screws to sit it in the focuser, that should help get it straight and centered.

You could also accept the tilt as native and constant, and work around it with collimation. From your image I think you secondary might be rotated a bit around the primary optical axis, so as a first step you could try to rotate it (loosening appropriate secondary screws) so that the primary image goes upwards and gets into the red circle.

21 hours ago, Gina said:

used it to backup the /dev/sda2 partition image

You should really save /dev/sda1 too, since it will have your distro's Grub2 boot files installed in it, and that will be touched by an upgrade or alternative distro install.

In theory for a real dist upgrade on Debians it should be possible to directly edit repository sources to change the distro's codename, then run apt-get dist-upgrade, but regarding Mint and possibly some system software (such as sysvinit / systemd) I'm unsure if it would work. Maybe try a two-step upgrade, first 18 to 19, then 19 to 20.

On 15/10/2021 at 20:02, Gina said:

I've used dd in the past and other tools.  Of course, to copy the system drive I shall need to boot from a Live Linux system, either CD or USB stick.

Any recommendations?

On 15/10/2021 at 20:52, Gina said:

Most of this I know of but section 4. TAR looks like a much simpler way than using a Live Linux USB stick.  It looks too good to be true.  Anyone done this?  Or any other comments.

Different ways for different needs :

• at filesystem level => tar, rsync. Will save your files efficiently with Unix attributes but not the structure of the system (such as boot files)
• at disk block level => partclone, fsarchiver. Will save your partitions efficiently (only used blocks of the filesystem) but require knowledge to manipulate.
• at device level => dd and clones. Will save all the raw disk blocks, hence not efficient at all.

For an easy backup solution I recommend RescueZilla (not to be confused with CloneZilla). It can save and restore efficiently your whole system or a subpart, all with a user-friendly GUI. But you have to boot into it for operations. I have given it to my father who has 0 linux knowledge and he copes with it.

Hi, I don't know about Mint, I recall it is or was an Ubuntu/Debian variant... so check with your usual package manager GUI (synaptic ?) for versions of packages "libc6" or "glibc", "libgcc..." or "gcc-libs" (unsure about the hyphen).

You can also look out on command line with commands like "dpkg -l | grep libgcc".

PS: I hope you kept the installer for the previous version, you may need it 😕

Edit : according to Distrowatch there https://distrowatch.com/table.php?distribution=mint your version 18 has GCC 5 and GLIBC 2.23 so I'm afraid that yes it's too old (latest Mint 20 would be required)

Hi, I rarely use this lens now but here is a sample I had with it :

A heavyweight DSLR such as D5500 on that delicate focuser... you're fearless ! 🤩

Nice M33 !

Loving its natural colors ... maybe raise low reds a bit for more nebulosities in the galaxy.

Can't be sure about the MPCC because I have the SWCC (which collar can't be removed -- softly), but from what I see you could use some small M48 extension (3-5mm ring or filter) camera side, so that it would be locked above the bevel.

It's quite cheap and would also make it sunk deeper in the focuser, and so would reduce the "protruding focuser tube" problem.