nfotis

Maybe a stupid question, but wouldn't a RASA or Hyperstar-equipped SCT be fast enough for a NV set-up?

N.F.

May I suggest iOptron CEM26 or similar?

Quite light, from what I read, and with the same payload as the HEQ5 or so.

Another possibility would be a harmonic drive, like the incoming ZWO unit.

N.F.

4 hours ago, The Admiral said:

If you mean can the tripod be used with other mounts, then it appears so. From https://www.firstlightoptics.com/category-537/zwo-tc40-carbon-fibre-tripod.html

 

"Developed for the new ZWO AM5 Harmonic Drive Mount but also compatible with mounts from the following manufacturers.

• iOptron
• Celestron
• Rainbow Astro
• SkyWatcher"

Ian

Intriguing, it may be a nice upgrade for other mounts as well.

For my HEQ5 mount it definitely is overkill, but I would like to try it.

N.F.

I wonder, would the tripod be used with other mounts as well?

N.F.

From what I understand here and the CN thread about the ZWO mount, it's a very lightweight HEQ5 class mount, with excellent portability.

An EQ6-R class mount (regarding load limit etc) seems to be in another price bracket.

N.F.

Interesting. Just discovered that they are a Greek company, will follow their progress with great interest.

N.F.

If we use an OAG, that should take care of the resolution limit of the guiding system, right? Then, we could see what's the accuracy limit of the mount, I suppose?

N.F.

What I understand is that ZWO is not promising better accuracy than 0.5 to 0.8 at seconds, due to the design and implementation of this harmonic drive.

A belt drive EQ6-R or CEM40 can run better than that, if I understand correctly, but not this mount.

N.F.

2 hours ago, The Lazy Astronomer said:

0.5 - 0.8" RMS is the typical guiding I get with my EQ6R Pro.

The guiding performance you need depends on your image scale. What camera will you be using with the C9.25?

Also, be aware that 1"/px is generally accepted as the limit for long exposure astrophotography due to the atmosphere, and even then, that will only be on the nights of the best seeing.

I am considering either the IMX533 or the IMX571 for DSO imaging. For planetary, I am using the IMX462.

Note that the claimed ZWO accuracy puts a floor (minimum) to accuracy. You cannot be better, even with guiding, while a CEM40 or an EQ6-R mount can do better (if I understand correctly).

At the moment, I own a HEQ5 mount, with no pretensions of doing DSO imaging (but I bought a 102ED refractor, which should work well)

N.F.

just saw it mentioned on the ZWO page:

"guiding accuracy is 0.5 to 0.8 arc seconds"

So, I suppose that puts a lower limit to the guiding accuracy, right?

Aside: If I want to use my C9.25 for DSO imaging or my Skymax 180, would a CEM40/EQ6-R and an OAG manage an accurate enough guiding? Or I would have to go to a pricey mount?

N.F.

Just noticed the label on a picture:

Telescope: 130mm APO with 900mm focal length. Image scale: 1 arc second per pixel, basically reaches the limit of the AMS mount. Thus, when photographing DSO objects, we don't recommend you use telescopes with longer focal length than this.

If that means I cannot use my C9.25 and Skymax 180 with that mount, that's a hard pass.

N.F.

PS. I don't know what's the limit of an EQ6-R, but I suppose that it should easily handle such scopes, even for DSO targets? I don't understand how these harmonic drives work, I suspect that there's some maximum control granularity which limits the mount to 1 arc second per pixel? Or 1000mm or so maximum focal length?

Interestingly, this guide dates from 2012... It took a decade to make the bird flyable.

N.F.

Car industry is testing new cars much more heavily than other consumer items, because each new car is being sold in the millions.

Astronomy is still a niche market, without many economies of scale etc. So, ZWO may have done some 'alpha testing' already, but it will take some time and effort/money in order to get a tried a proven product. On the other hand, there's already experience with other mounts, so I suppose that they kept detailed notes of the good and bad things in previous implementations.

The whole system has the main advantage. Imagine an EQ6-R class mount, but weighting only 5 kg, and at nearly similar price.

What's not to like? Obviously, a few things.

We will have to wait, in order to find out. It seems that such drives require guiding in order to work well, you cannot depend on unguided performance. On the other hand, these promise zero backlash. Also, a loss of power could mean our scope toppling with the mount (ZWO claims an automatic brake for such an eventuality).

Waiting with interest for the reviews.

N.F.

EDIT. There's also a Sharpstar harmonic drive mounts in the wings:

http://www.sharpstar-optics.com/index.php/en/customization/389.html

1 hour ago, Alien 13 said:

I am scared now, would feel safer with a Musk or Russian launch 😱

Alan

ESA participates on the JWST mission with the contribution of an Ariane 5 and two of the four instruments, so the telescope was forced to be designed within the volume and mass constraints of the Ariane 5 fairing and mass capabilities. NASA, ESA etc contribute to each other's mission usually 'in kind', without money being exchanged. Also, note that SpaceX wasn't available when JWST started being designed (and the recent launch failures of the Proton didn't inspire much confidence, I suppose).

The management of the JWST project by NASA was a near disaster, as the mass budget was exhausted quickly, and there was no room for making a more robust sun shield system. The cost skyrocketed as a result, and JWST has been termed "The scope that ate astronomy", because all the NASA budget available for the various astronomy projects has been drained by this program.

If the launch and mission is a success, few will complain. But the hard lessons from the JWST management haven't been lost on NASA on other groups, with WFIRST telescope (based on a donated tube from NRO) was more tightly managed, and when mission creep raised its ugly head, there were measures to limit the scope to the original specifications.

There are two nice press kits in multiple languages from Arianespace and ESA (I put the English versions below):

https://arianespace.com/wp-content/uploads/2021/12/VA256-launchkit-EN.pdf

https://esamultimedia.esa.int/docs/science/Webb-LaunchKit_EN.pdf

N.F.

On 17/12/2021 at 03:28, johninderby said:

A repair mission would be possible if NASA got the billions in funding that would be needed but might be cheaper to build a new more advanced telescope. 

JWST isn't repairable.

It isn't designed for that, in contrast to Hubble (the latter had lots of grabbing irons and oversize screw heads for handling via astronaut thick gloves etc).

You see, because they exhausted the JWST mass budget very early early (mission creep and all that), they had to cut weight everywhere. And that included removing screws everywhere possible.

So, they are using mostly glue for the assembly of the scope. If they found some broken item, they would have to disassemble (unglue) it first, replace the problematic items, then reassembly using glue etc. And there's just no way to replace subsystems in it, no rails and slots for that - it's extremely tight integration.

Even if a spaceship was able to reach JWST in the destination place/orbit at L2, how would it approach it without the engine exhausts damaging the extremely sensitive instruments? *Maybe* they could refuel the cooling liquid in order to keep one of the infrared instruments in operation. Maybe they could manage to refuel it in space etc.

I am pretty certain that JWST will be the last of its kind (and first). In the near future, boosters like the SpaceX Starship, Falcon Heavy, Vulcan, New Glenn etc could offer a much higher mass budget, which could permit a more robust and cheaper construction, with redundancy etc. A great part of JWST's cost came from testing and redesign within the strict mass budgets. Imagine if you had 60 tonnes of mass budget instead of 6 - you could use a heavier steel construction instead of exotic stuff, much more robust mechanisms for the sun shield, add cameras around the scope for self-monitoring, add 10 tonnes of fuel for orbital maneuvers etc.

N.F.

Quite intriguing.

It remains to be seen what features and price will be attained. I guess that they will position the new camera a bit below the IMX492?

N.F.

From what I understand, their main attraction is lower weight.

But you need a really good tripod in order to avoid the scope tipping over.

Also you are required to guide with these mounts, and I have the feeling that this technology is still not quite refined compared to conventional mounts.

And these are quite expensive still.

N.F.

You don't need a high end laptop for image capturing and controlling mount, filter wheel etc. Heck, even a slow Raspberry Pi has enough horsepower for this, and it's cheap enough you can dedicate it solely for astrophotography purposes.

For processing, CPU and memory are major parameters. It may be a better idea to use a desktop computer with eg a Ryzen 3 5700G processor (eight cores, 16 threads) and 32+ GB RAM instead of looking for a pricey high performance laptop, which soon will be thermally throttled as you are hitting it with heavy processing.

N.F.

The RisingCam stack has definitely a lighter background at the top half of the image, I suppose that's due to a different offset setting for the black point?

I don't know if the IR/UV cut filter can influence the end result so much?

N.F.

9 hours ago, gorann said:

This is a bit off topic but I was looking through the Risingcam web store (through Ali Express) and found that they are selling a camera with the IMX410 colour sensor. This is the same 24 Mp (6 µm pixel) full frame sensor as in ASI2400MC or QHY410 but at 75% of the price (about 2600 Euro without VAT if I calculated it right). An excellent sensor as far as I can tell with big pixels (104 ke- well depth) suited for longer FL scopes. I guess no one here has pulled the trigger on it yet.

https://www.aliexpress.com/item/1005002530783852.html?spm=a2g0o.store_pc_groupList.8148356.32.4b1a243fqbSqjY

They are also offering the equivalent of the ASI 6200, I think (IMX455?).

In reality, I suspect that not many people have a need for a full frame sensor (and its costs regarding filters, tilt, etc)

N.F.

Quite interesting comparison, thanks for the demonstration. I suppose that there's a need for some settings optimization still?

N.F.

This blog post gives you a list of possible ways to mount a guide scope to the 102ED 

https://www.svbony.com/blog/How-to-mount-SV106-to-SV503/

On 04/12/2021 at 19:48, Toltec said:

Ordered one from Altair this morning. Slight mission creep, started looking at binoculars, then decided a cheap 100mm achro might be better and ended up with one of these...

Don't worry, that happens all the time 

(I sympathize, it has happened to me as well)

N.F.

The weather is still quite variable, so I shot some indoor photos of the scope.

My observations (this is my first ever refractor):

- quite a plain packaging outside, quite good plastic cradle inside (a corner had been cut in order to fit the flattener/reducer package inside)

- Surprisingly large, the photos don't do it justice (I included a DSLR camera with a 70-200/2.8 lens and a soft drink, to give a sense of scale)

- The dual speed focuser side had its own plastic cover, I suppose that it's installed in order to protect it while in transit.

- No manual/documentation included. As this is a OTA only package (no diagonal, finder or eyepieces included), you are expected to know which end of the tube goes in front 🙂

- Subjectively, it feels quite well built (a few dust bunnies on the front elements were blown away easily). The focuser includes also a rotator, so you can frame your target as you well please. A built in retractable shield should help with reflections and dew. The large ED glass element in front has a greenish cast.

If I manage to find some time tomorrow, I hope to shoot some land targets at least.

Cheers,

N.F.

extremely detailed, I haven't finished it yet (too much material to digest).

There's also a companion on solar observation and imaging (waiting to receive it)

N.F.