ZWO at NEAF 2023

Kentmd

It was great to see ZWO at NEAF live! First live NEAF since 2019. It was so nice meeting Simon and the rest of the staff. Some amazing
new ZWO products. In fact I went home and ordered the new 107 mm APO refractor 😁. I have until June to save up $$$. Simon’s talk in the Field House Theater was excellent and it was a pleasure to meet him.

Clear skies!

Ken

w7ay

Kentmd In fact I went home and ordered the new 107 mm APO refractor

You do know that is just the Askar 107PHQ that has been rebadged, don't you?

Chen

Kentmd

w7ay No I don’t know that.🙂

Kentmd

w7ay So we can say I’ll be 100% ZWO when I get it and got the reducer free👍🏻😁.

w7ay

Kentmd I get it and got the reducer free

Be aware that you will get substantial red/green fringing at the edges and corners of an APS-C and full frame camera with the Askar ("ZWO") reducer:

Notice that not only is the spot diagram bloated from 2.77 µm RMS radius at the center to 9.43 µm RMS radius at the corners of a full frame sensor, the green and red components are separated by 20 µm -- that is 5.3 pixels worth of chromatic aberration on a ASI6200 camera. Even the corners of an APS-C sensor (like an ASI2600) already shows large chromatic aberration (the GEO radius shows it).

The bloat of the spot diagram at the full-frame ASI6200 corners makes the star have a FWHM of 5 pixels, with green and red components separated by about 5 pixels.

(GEO radius is the radius where rays of all wavelengths fall into. Notice that the corner of an APS-C frame is not that much better -- 13.8 µm radius or polychromatic FWHM of about 7.3 pixels for a ASI2600, and 17.9 µm radius or polychromatic FWHM of about 9.6 pixels for an ASI6200 camera.)

https://mercaph.github.io/2020/11/19/ZEMAX-notes/

I'd assumed that you have already checked all these out before ordering the OTA.

Chen

Kentmd

w7ay Thanks for the info. This is all very technical but what you are saying is there are issues with the stars in the images.
Simplistically I’d say what is the point of buying another APO that has star fringing or whatever, especially I already have a Borg that is superb. Only it has a helical focuser so I can’t use EAF unless there is an adapter for that. The ZWO scope is back ordered so I can easily cancel.

w7ay

Kentmd Only it has a helical focuser so I can’t use EAF unless there is an adapter for that.

Yes, you can. With standard brackets from ZWO, even.

This is how I attached an EAF to a Burg Helical Focuser (which is practically useless manually). But the EAF gives it enough resolution to make it work:

https://bbs.astronomy-imaging-camera.com/d/16207-alternate-eaf-mounting

You need to drill and tap two holes in the EAF, but I did that even with a hand drill. The EAF body uses very thin and soft aluminum.

https://bbs.astronomy-imaging-camera.com/d/16207-alternate-eaf-mounting

There are multiple sources for the rubber ring gears. One is even on Amazon:

https://www.amazon.com/dp/B0986MSLRP
https://tilta.com/shop/seamless-focus-gear-ring

They are used for video production using handheld DSLRs.

The real solution to the focuser is to use an Starlight Instruments' FTF -- they have one (with 0.8 inch travel) that fits a 80mm Borg tube with M57 instrumentation end. I have a couple of them. And it is easy to attach an EAF to it.

I still have the fluorite Borgs 55FL, 71FL (yes, the old 71, not 72FL) and 90FL, and then switch to Takahashis after that for even better quality. So I just use the 55FL as a guide scope nowadays. For Solar H-alpha, I switched from the 71FL to a Takahashi FOA-60Q and for deepsky, I switched from the 91FL to a FSQ-85.

Chen

Kentmd

Nice assortment of gear! I have the Borg 77 ED I won at NEAF many years ago. I’ve been manually focusing but will definitely look into you great suggestions. Hopefully I can avoid drilling my EAF😂.

Thanks so much!

w7ay

Kentmd Hopefully I can avoid drilling my EAF

Nothing to it. I used a hand drill with one of these contraptions:

https://www.amazon.com/36-37-Precision-Portable-Lightweight/dp/B00004T82L

Just measure where the holes are carefully to make sure there is enough clearance. I used M4 screws, and have boxes of them of different lengths.

The EAF uses very thin aluminum for the shell. Almost all the weight is the stepper motor itself.

By the way, I also drill into Borg tubes.

I had been using the Borg 7517 tube that has a mount with the 55FL without the reducer. But the 7517 is too long (60mm) to use the reducer of the 55FL objective. So, I took a Borg 7603 (40mm long) and drilled and tapped it to take the legs of the Borg 7517. And then also drilled and tapped the 7603 to also take the ZWO EAF long plate. So my 55FL guide scope current configuration looks like this (helical focuser being used as a front focuser):

(The Baader VariLock is to dial in the backfocus of the 55FL reducer (Borg 7880).)

If you have a Borg, you might as well take full advantage of it (like being able to drill into tubes).

Chen

Kentmd

There are various sizes so not sure which would work this is 2 inch with .8 inch draw is this what you mean?

https://www.starlightinstruments.com/product/ftf2008bcr-feather-touch-rotatable-2-0-diameter-dual-speed-0-8-draw-tube-travel-brake-and-compression-ring-aka-shorty/

w7ay

Kentmd There are various sizes so not sure which would work this is 2 inch with .8 inch draw is this what you mean?

The 2" FTF comes in various styles. The common part is that they all have the same dovetail to attach to the OTA end (also doubles as a rotator to orient the knobs).

If you buy the "Borg version" of the FTF (FTF2008B-M57), you get the adapter shown above. The thread is the M77.6 thread that Borgs use for their 80mm tubes. The drawtube of the "2008" FTF has 0.8" travel (the "2015" has 1.5" travel, etc).

The drawtube of the Borg model is threaded at the "camera end" with a male M57 thread (thus "Borg").

If you prefer to get a 2" eyepiece holder at the camera end, you can buy any of their other 2" FTF, but specify that you want the M77.6 adapter for the telescope end.

You can also get the adapter from PreciseParts.com, by specifying 2" FTF to Borg M77.6. I have a PrecisePart adapter instead of the one from Starlight Instruments for a Mewlon, since I wanted a shorter FTF adapter than the one Starlight sells for the Mewlon.

The M77.6 thread is really only useful for the 80mm Borg tubes. The FTF is really large and heavy for adapting to the Borg 60mm tubes.

For the 2" eyepiece holder on the camera end, you can get other drawtube lengths. The FTF2008B-M57 is equivalent to their non-Borg "Shorty", with 0.8" travel. For the 2" focusers, they also have models with 1.5", 2" and 2.5" travel. Additionally, Starlight have models where some of the metal is hollowed out to be lighter (perfect for the Borg lightweight paradigm -- so I have one of those too).

You can pretty much mix and match FTF stuff, even though it does not show up on their web pages. Just email them.

If you remove the FTF focuser lock screw, you can attach a ZWO EAF plate to that.

If you don't care about ASIAIR compatibility and want an electronic focuser, Prima Luce makes a really nice one (Esatto) that has adapters for Borgs (2" version for 55FL and 3" for 90FL and 107FL). Check out Ishikawa-san's web site digiborg.wordpress.com.

Chen

Kentmd

Thank you Chen.