Dithering without EQMOD etc

[xa-coupe]

I'm having a wild time trying to figure out why my guiding has gone nuts, so to test out the mount I have plugged the hand controller in (after a sharpcap polar align) and are easily getting 60s subs with no trailing... so I think it's safe to say it isn't the mount. Whilst I'm letting it run out 200 subs (of 45s to be safe) to ensure that it isn't a transient issue, I have been trying to figure out if it's possible to dither without using a separate controlling program.



So far, nada .. has anyone got any ideas?


Oh, I can't go look at the handset as I image from a deck and the smallest movement causes chaos.

[Startrek]

Jeff,
For dithering to be effective in reducing fixed pattern noise , the movement of each frame should generally be in a random or spiral pattern of pixels up to a certain amount , usually calculated from a ratio and multiplier between the image scale between your imaging camera and guide camera ( generally movement of frames are not in a direct horizontal or vertical pattern )
I don’t know if you can successfully dither without a software designed program as the dither function and movement is not guess work , there are sophisticated algorithms involved to enable it to be effective.
Just remember guiding can be “wild” or poor one night and fantastic the next
My guiding numbers on Saturday night were 0.65 to 0.75 arc sec total and last night were 1.15 to 1.35 arc sec total ( huge difference) same set up and both nights clear , no cloud
If your using PHD2 guiding ,I recommend you post your guide logs to the forum so they can be analysed.As your probably aware when guiding goes a bit haywire it can be attributed to -
Periodic error ( mechanical )
Mount Balance
Cable snags
Wind
Cloud
Atmospheric turbulence
Humidity and Dew
Altitude
Flexure
Guiding set up and parameters
Vibration
And so on ......

Not an easy fix but can be evaluated in time
Cheers
Martin

[xa-coupe]

Thanks Martin. My guiding didn't just have a bad night, it went totally wild. I was used to .5-.6 RMS error on a good night to .8 on a bad night then it was throwing 2.x for days on end no matter what I did.

I've adjusted the backlash out, spent on a pegasus power box to shorten cables and so on ... all to no avail. I've ordered replacement cables for anything that could possibly be related ..but in the mean time I am getting comfortable with the handset again!

[Startrek]

Jeff,
Wow that’s a wild mount
Is your imaging rig payload no greater than 60% of the mounts max capacity ?
Maybe do a re calibration near the north meridian and celestial equator ( ie: declination close to zero )
Here’s some attachments I put together for PHD2 and EQMOD.They may be of some help ??
Martin

[xa-coupe]

Thanks Martin, those documents are what helped me get me into my initial EQMOD foray.


After a couple of hours of perfect performance with the handset, I wired it all back in and it pooped itself. I suspect a faulty FTDI/EQMOD cable. 3 different PCs and same problem and it's quite unlikely to be the mount given tonight's efforts.

[Retrograde]

Hi Jeff,
You can do manual dithering from PH2 if that's what you mean?
It's done from: Tools -> Manual Guide.
You can select different settings to vary the amount of dithering you want.

[xa-coupe]

Thanks.. I was hoping to write PHD2 out of the equation... my guiding issues are driving me nuts. At least with sharpcap's polar alignment I can do decent relatively long unguided images.

[toc]

Perhaps NINA is an option? It appears to support Dithering without having to guide:

"There are cases where there is no guiding equipment in use, and thus no PHD2, but where dithering is still desirable. Examples of configurations like this usually include small, portable setups that have a main camera and telescope or lens, but no guiding. In cases like this, N.I.N.A. can still effect dithering operations, but on its own through its Direct Guider facility. Once activated, dithering operations become available in the Sequence and are effected by N.I.N.A. directly."

No idea if it works, but might be worth a try.