RedCat 51 first image - Oh No!

[FLO]

7 minutes ago, Nubian said:

I purchased from FLO but Im still waiting for delivery.

The latest info regarding availability can be found here ? 

8 minutes ago, Nubian said:

I was just curious how possible issues will be handled

You are worrying too much. 

So far, Alan's RedCat is the only one returned to us. 

HTH, 

Steve 

[Nubian]

Well, his replacement has shown the same coma.

But you are right. I'll relax now and look forward to my first telescope ever! Im a real noob on astrophotography and I'm so excited to hold this thing in my hands soon

It took me quite a while to get into this hobby. This picture shows myself in 1983 or so with my hands on my fathers balcony mounted refractor

 

[Davey-T]

Took first star images with the RedCat last night before the Moon rose, a few shots of asteroid Pallas.

All the stars across the whole image have what looks like a blue coma effect going from right to left, terrestrial South to North, haven't done any more investigating but not looking too good ATM.

Dave

Crop of the central stars

 

Edited April 22, 2019 by Davey-T

[symmetal]

No that doesn't look good Dave.  On my 2 Cats the central stars were very good. On your reduced scale first image there is visible coma too, on the right hand side.

I haven't heard any feedback results yet after my RedCats second visit to Es' Reid. 

Alan 

[Davey-T]

Nice clear skies last night so did some testing, here are the results cobbled together in P'Shop, as can be seen unfortunately the RedCat is going to have to be returned.

All 30secs ISO800 Canon 60Da on Star Adventurer

Dave

Canon 300mm

WOZ61

RedCat still got little blue shuttlecocks across the whole image

 

Edited April 26, 2019 by Davey-T

[symmetal]

3 hours ago, Davey-T said:

Nice clear skies last night so did some testing, here are the results cobbled together in P'Shop, as can be seen unfortunately the RedCat is going to have to be returned.

Dave

Thanks for the comparative shots Dave. The RedCat comes a poor third.  Same direction coma over the whole image is what I get with the majority of my camera lenses, especially the Samyang 14mm. Are you going to wait to see if Es' Reid can fix them. Taking a chance on a replacement maybe too risky. I've PM'd Steve at FLO to see if he knows whether Es' has managed to fix my first RedCat. If so, I think WO should reimburse FLO for the costs in having to send them to Es'.

The Canon 300mm looks good but as I also have a WOZS61 the difference in focal length is not that great to warrant getting one I think. I'll probably look at a 135mm or so lens to fill the gap. .

Alan

[ippiu]

Hi to everybody.

I have the beatiful gem RC51. And i'd like to investigate if it has the coma issues present in some previous models.

I took flat frame. I took a couple of quick images last week before the weather broke forever in .png (i forgot to change the file extension in .fit in Sharpcap).

i'm asking everyone a favor: could anybody take a look at my files and say if my RC51 is good? I would really appreciate if someone, more expert than me, could have a look at my pictures.

As soon as the weather will be fine (i hope soon...) i will have another test session taking .fit images...

https://drive.google.com/open?id=1NnDBIFAQQLa08hZo3fcv9auwLiD48pRz

Thanks so much

Edited May 14, 2019 by ippiu

[symmetal]

Hi ippiu,

I'd say you're RedCat is a good one.  There is a hint of coma on the extreme bottom right but nothing that would cause alarm. The CCD Inspector analysis below indicates a slight sensor tilt from left to right which could be the reason for making the stars bottom right and top right very slightly misshapen as they end up being slightly out of focus. I assume this is using a DSLR?

Overall I think you've got a winner. Better than I and Davey-T have.

Don't worry about the first analysis looking worse than the second. Visually there's little between them.To get a proper analysis you need to take the average of several images.

Alan

[helgeras]

Hi,

could you comment on mine too? I can see some coma in the left side, but I am not an expert, so I do not know if this is ok, or if I should send it back.

 

The following directory contains a fit, sony raw and jpg of the same snapshot. It also contains a screen grab of CCD Inspector for the same picture:

https://drive.google.com/open?id=1Js6dSv7aCG9NADZ_lB9IbPkhuAVKXO7q

 

Thanks in advance,

Helge

[symmetal]

Hi helgeras,

Yes, I'm afraid there is significant coma on the left third of your image as the CCD inspector image you've posted also indicates. CCD Inspector reports poor star shapes as indications of curvature and/or tilt though this is not always the reason for poor star shapes, coma being one of them. As I've found, the coma can't be improved by different focus so curvature/tilt is not the problem. I would say your RedCat needs to be returned. .

Alan

[ippiu]

@symmetal Thanks, thanks, thanks so much.

Analyzing all my pictures (i have many in .png, but i chose 2 images to upload) at 200% on pc screen i had the same your impression: the right side is the worst expecially the corners.

But i'm not completely satisfied with my Rc51 because i'm using only a  relatively small 4/3 sensor (Asi294): even if the coma effect is very little, it shouldn't be there. Because William Optic says "the sharpest lens ever made for full frame": false

How big would coma be on full frame sensor??

I have uploaded several more images. Could you please analyze any of them? I haven't ccd inspector.

https://drive.google.com/drive/folders/1NnDBIFAQQLa08hZo3fcv9auwLiD48pRz

So i could decide if keep RC51 or return it to seller...

I'm so grateful to you @symmetal

[symmetal]

ippiu,

The ASI1600 which I used when posting my test images is also a 4/3 sensor and they were significantly worse than yours. Using a full frame sensor the coma effects should get increasingly worse towards to corners though I haven't actually tried it so can't give you an accurate answer. Do you have a DSLR to compare it with. An APS-C is significantly larger then 4/3 so should show the worsening coma effect and give you an idea how the full frame might look. I'll examine your other images a bit later and report back. I think the WO claim is that it's the sharpest 250mm lens for full frame but as there aren't any others to compare it with, it can also claim to be the least sharp lens too. 

At the moment it seems to be a lottery as to what quality lens you get and if you get yours replaced you could easily end up with a worse one.

Alan

[ippiu]

10 minutes ago, symmetal said:

I'll examine your other images a bit later and report back. 

if you get yours replaced you could easily end up with a worse one.

Alan

I look forward to seeing here the results about my new images analyzed by your CCD Inspector.

And i thank you so much in advance.

I have time until next monday to return it to seller and ask for a complete refund. So according to your CCD Inspector analysis i decide if to keep it or to return.

I don't want to risk in an another worse replaced RC51 model...

If i decide to return it, I would try this: https://www.teleskop-express.de/shop/product_info.php/info/p11067_TS-Optics-61EDPH---5-Element-Flatfield-Apo-61-mm-Aperture-F-4-5.html

[symmetal]

Hi ippiu,

I examined your 10 120s images and 10 180s images and they have all very similar star shapes, (if not exact). Here's the CCD Inspector curvature and 3D plot results of the average of the 10 120s images. The 180s images were the same. The pixel scale was assumed as they were png files so the arc-second values are not accurate though relative to each other it gives an idea. Also it is treating the coma as defocused stars so the actual curvature and tilt values don't really mean much. There is slight coma down the right hand side with the bottom right being the worst as before. When stacked and processed including debayering, it will give you a better idea of what the overall image is like and whether it is too noticeable. Many people would be happy with it, but only you can decide whether you are. It's not perfect, and you usually have to pay a lot more to achieve anything near that. Have you seen any images from the alternative scope you're looking at to see if it might give better results.

Alan

[ippiu]

@symmetal

Thanks really so much...Now i know that my Rc51 model is not perfect, but acceptable, passable.

You say "Many people would be happy with it": I'm not because i bought this scope with just in mind to take large portion of the sky and so i didn't plan to crop the final image.

"Have you seen any images from the alternative scope you're looking at to see if it might give better results": Not yet. But few months ago i owned Sharpstar 86Q quadruplet and Ts 100Q quadruplet: they didn't show any sort of  issues as those one present in RC51. 

In the next few days i'll have to decide...

[happy-kat]

But were the quadruplets not quadruple the price of a Redcat?

[souls33k3r]

28 minutes ago, happy-kat said:

But were the quadruplets not quadruple the price of a Redcat?

There was never a 51mm quad, the closest were a 65mm and a 70mm and the answer to being quradruple the price of the redcat ... again no.

[Adam J]

8 hours ago, ippiu said:

@symmetal

Thanks really so much...Now i know that my Rc51 model is not perfect, but acceptable, passable.

You say "Many people would be happy with it": I'm not because i bought this scope with just in mind to take large portion of the sky and so i didn't plan to crop the final image.

"Have you seen any images from the alternative scope you're looking at to see if it might give better results": Not yet. But few months ago i owned Sharpstar 86Q quadruplet and Ts 100Q quadruplet: they didn't show any sort of  issues as those one present in RC51. 

In the next few days i'll have to decide...

I am very tempted by a Sharpstar 86Q, its on my short list of scopes for when I finally get the cash together. Example images showing corner stars would be appreciated. 

Edited May 15, 2019 by Adam J

[ippiu]

8 minutes ago, Adam J said:

I am very tempted by a Sharpstar 86Q, its on my short list of scopes for when I finally get the cash together.

Great scope. I exchanged it for Cem25 EC... This is it (still unsold): https://www.astrottica.it/demo-e-usato/3081-rifrattore-apocromatico-sharpstar-86sq-f-54-quadrupletto-fcd-100.html 

8 minutes ago, Adam J said:

Example images showing corner stars would be appreciated. 

All images taken with Asi294 and 86SQ: https://drive.google.com/open?id=1p0zs2_G61OvRNCaSt1kuY-qU2AWiWd7G

[Nubian]

My RC also arrived this week! 😀

Do I need to take several images for the coma test? How do I evaluate the results correctly?

Someone here uploaded a fits file. What is it important for?

[Davey-T]

3 hours ago, Nubian said:

My RC also arrived this week! 😀

Do I need to take several images for the coma test? How do I evaluate the results correctly?

Someone here uploaded a fits file. What is it important for?

What mount / camera are you using ? a single DSLR image of around 60 secs is needed to get maximum field of view.

Uploaded file can be checked for " flatness "

Dave

[symmetal]

4 hours ago, Nubian said:

My RC also arrived this week! 😀

Do I need to take several images for the coma test? How do I evaluate the results correctly?

Someone here uploaded a fits file. What is it important for?

As Dave said a single image is all you need. As the coma, if present, is usually more evident on the edges of the image, a larger sensor (as on a DSLR) will show problems which may not be apparent on a small sensor.

If there is coma you can see it yourself visually when examining the image (especially in the corners) where the stars have fan shaped smears from the star centre. If you can't see any you're lucky and have a good lens.

A fits file is the normal file format from astro cameras and the fits file header includes useful information about the image but isn't necessary. From a DSLR just convert its output file to a tif or png file, which CCD Inspector can read. I'm not sure if it can read DSLR raw files. The CCD Inspector just gives a more accurate display of the star shapes/sizes though will interpret coma as a curvature/tilt problem though that is not always the correct interpretation. The coloured CCDI plot is very useful as a quick check that the image is good or has problems.

Alan

[ippiu]

Today I returned to seller my RC51 and asked complete refund.

Probably returned also cem25EC: as present in RC51, problems also on this mount, after days of test: https://www.cloudynights.com/topic/660863-cem25-ec-03-arcsec-rms/

So i'm frustrating that i'm thinking to sell everything and probably go back to peace: visually with Cpc925.....maybe...

[symmetal]

Hi ippiu,

I see you've decided to return the RC51 and the CEM25EC mount (having read the lengthy discussion on CN). As the final CN post says it's easy to get too involved on tests and not actually check what the final images are like after having stacked and processed many exposures. You may have found the slight edge coma shown in your test exposures would have been masked by the final stacked/processed image result and been hardly noticeable. Likewise with your mount. To get 'technically perfect' images you would have to spend a lot more money on the equipment, and so have to accept that there will be some flaws with your current setup, or any future setup that costs a similar amount.

I agree that the RC51 shouldn't show coma and WO should really have this fixed before they released them, as it just seems to be a setup alignment problem, but yours was one of the better RC51s. Look at Davey_T's or helgeras' images to see what a poor RC51 looks like.

Hope you manage to get something in the future that you like. 

Alan

[JimothyC]

I took advantage of some clear weather yesterday to give my RedCat a test out. Reading all the stories about collimation issues had me worried that I might have bought a turkey. Coincidentally it was also the last night with a shred of astro-darkness, so I had to move fast. 

Picked M101 as a target as it was nice and high up in the sky. In the rush my filter wheel stopped working, so I was stuck with just luminosity frames. 

Setup was a RedCat on an ioptron CEM25p. Camera ZWO ASI1600mm, EFW7, Baader 36mm filters, ZWO mini guide scope and ASI120mm guide camera. 

I'd really appreciate it someone could have a look at my attached image and give me their opinion on the star shapes. I'm no expert in this, but to me it looks like there's some coma and there's something definitely odd going on with the brighter stars. 

Attached file is a png from sharpcap as I was livestacking during testing.