A step up from NexImage

[26Left]

Hello,

I've spent the last nine months experimenting with a Celestron NexImage. I think my results on Jupiter and Saturn are quite reasonable, but, as always, I know there is room for improvement. I have spent enough on telescopes, but a new camera is within reach. I would really appreciate some advice before I go out an buy a DBK, which I have read is good.

Saturn is a tough target compared with Jupiter, because it is dimmer. My scope is a 5" Meade triplet. It's a great scope, but doesn't collect as many photons as I'd like. I am working at F/26, which gives me an image scale of 0.34 arc seconds - reasonable for my scope if the seeing is good.

The attached "capture.jpg" is one frame of the video stream. Brightness on the driver was set half way, as was gain. I recorded at 5FS and exposure was 1/5s. The histogram peaked about half way along. As you can see, it's rough and noisy. Through the magic of Registax and PS, "Saturn1.jpg" and "Saturn2.jpg" were the results. "Saturn2" is perhaps a little overprocessed, but I wanted to bring out the storm in the north.

So, the crux of the matter: would a DMK allow me to image at say 10FPS? Since it uses the same imaging chip as the NexImage, my gut feeling is that is cannot be anymore sensitive than the NexImage, but perhaps I am missing something. I cannot push the NexImage to 10FPS on Saturn because it gets too dim, but could I do this on the DBK?

I have read in some places (but not the Celestron manual) that the NexImage should be restricted to 5FPS to avoid compression. I am also uncertain whether the USB interface is v1.1 or v2.0. Jupiter is brighter and I can see an advantage in the DFK if I can record at 10FPS or 15 FPS. Not sure if there's much advantage with Saturn unless either the DBK is more sensitive than the NexImage or generates less noise.

One last thing: I use eyepiece projection with a Baader Hyperion to achieve the image scale. I would prefer to use a barlow (less glass, less CA etc.). I need to magnify by 3.5. Any advice? Perhaps a 3x Televue Barlow?

Thanks for reading this long post!

[Space Cowboy]

Very impressive images for eyepiece projection on a 5" scope! At first I thought they were taken with a DBK lol. I'm surprised you can't go above 5fps....I would suggest using higher gain, some people use 100% gain as long as you take a 5-6 min avi the amount of frames will solve any noise problem. I use a spc 900 and I'm also debating whether to get a DBK as like you say it has the same sensor. I have been reliably informed that a dbk will capture at 30 fps which in theory makes it about 3x better i.e 3x more good frames. As you say that may only work with Jupiter.

[26Left]

Thanks. Higher gain and 10FPS is worth a go. I'll try it. The pics were taken on 22nd. April and the seeing was exceptional. Never been repeated since, which makes comparison of different configurations all the harder!!

[blackparticle]

Great results.

I'm curious, how many frames of AVI video did you process to achieve the final image?

[26Left]

It was a 3m25s run at 5FPS. I kept about 85% of the frames. So, about 850 frames I think.

It was my first time using Registax after upgrading to version 6. Registax 6 seems to produce better images for me than v5, but that may just be because all the settings when back to their defaults after the installation!

Seeing was exceptional. I remember, because I got the family out to look at Saturn, which was due south. Sadly, it has been downhill since then

Cheers,

Tom.

[AztecastroMcJ]

great results esp for small aperture and ep projection, which i have never tried

most use 10fps with spc any higher compression is noticed

for prime focus with barlow u will need to use 1/25 exp and full or just off full gain

most get televue powermates, or celestron ultima x2

imagemate x4 and revelation astro 2.5x i have and are both great value as is tal x3

i cant get Saturn bright enough using x3 f/36

so i am using 2.5x f/29.5 and ocassionally use extension in better seeing

had some great views this week aswell

thx for posting

James

[26Left]

Aztecastromcj: Thanks for the advice. I got hold of a 3x TeleVue Barlow today, so I'll give that a go. I've got the x2.5 PowerMate, but, you cannot increase the magnification by using an extension tube, so I thought I'd try a barlow. I'll give 10FPS a go. I've never tried before.

Which brings me back to my original thought: would a DBK be better? Same chip as the SPC/NexImage. So is the only advantage the FPS? Or is there more to it? The box is a nice shade of blue

Cheers,

Tom.

[KEJ]

Tom blimey great images, my finals are more like your captures. I must admit I have tried Registax 6, but more often than not it works through fine, but I end up with a black screen, two out of three - very odd using the same clip.

Great pics

[KEJ]

Breaking news Registax 6.1.8 update and it fixes the problem I had:

Solves the following issues reported:

- debayering often leads to dim nearly B/W images after stacking

- RGB-Align causes red/blue image-edges in the resultingimage.

- when LRGB is checkmarked (at stack) the final image at wavelets is black.

- Avi's that have a non-zero starting position (reported when the AVI is loaded in Virtualdub) do not load.

- centre of rotation (at wavelets) cannot be set

- loading a previously saved Gamma doesnt work

[AztecastroMcJ]

Aztecastromcj: Thanks for the advice. I got hold of a 3x TeleVue Barlow today, so I'll give that a go. I've got the x2.5 PowerMate, but, you cannot increase the magnification by using an extension tube, so I thought I'd try a barlow. I'll give 10FPS a go. I've never tried before.

Which brings me back to my original thought: would a DBK be better? Same chip as the SPC/NexImage. So is the only advantage the FPS? Or is there more to it? The box is a nice shade of blue

Cheers,

Tom.

hi Tom

Dbk would be better as Stuart as suggested for increased frame rate 30fps,

mono versions are more sensitive but would require buying filters aswell,

and more captures and processing

another option is to wait for new more sensitive IS cam due out soon with 618 chip,

this chip is best for sensitivity and most top planetary ap's are using in them in flea3 cam

u can also get the colour chip in your neximage, replaced by 618 chip but u would be limited to 10fps,

if u dont want to mod urself someone like astronimiser will do it for you, the dmk can be modded aswell allowing for 30fps with 618 chip

something i have been wondering about myself recently

James

[26Left]

Thanks James. Yes, I read IS's announcement last year I think. Don't know when the launch date will be though. Ah well, I'm in no hurry!

I tried 10FPS tonight, but got clouded out. I'm not sure I could go much faster than that anyway, because I only have a 5" scope, so I need to keep exposure time higher than I'd like.

Thanks again.

[Kokatha man]

I think you'll find the DBk is quite a step up on the Neximage etc.....the faster framerates achievable through the electronics and the usb2 interface will be salient factors: Saturn can be imaged at very low histogram/exposure settings (40-45%) so it's not inconceivable that even with the limitations of your aperture you'll find faster framerates possible.....and at the scale you're working with you really should take the full 6 minutes of imaging runs to again maximise the frames collected.

You've interposed DMK, DBK & DFK in your posts a bit (typos?) but as I'm sure you'd know, the DMK is the mono unit requiring filters etc and the DFK has an inbuilt filter that differentiates it from the DBK.....it'd be the DBK you'd go for in a colour cam (I had one and was extremely pleased with it untill I upgraded to the Flea3...)

But as James has mentioned, the new TIS cameras that are supposed to be coming out fairly soon (but who knows when exactly?!?) will feature the much more sensitive Sony ICX618 chips that the Flea3 uses.....remembering though, that most of the increased sensitivity is in the red.....

The usb2 interface and onboard electronics of the current DBK21 are what makes it a big step up from the SPC900 and Neximage type cams imo.....that and of course the ability to utilise greyscale transmission with Y800 codec out of this cam.

[26Left]

Thanks for your helpful reply.

Yes, I'm getting myself confused over the model numbers. I'm thinking of the colour version without the IR filter. I'll work it out!

Interesting that you mention that you can keep the histogram settings low. I have found that I get better images of Saturn with the histogram peaking about halfway that by getting an almost full histogram. The same was not true when I was imaging Jupiter last year. Perhaps it is because the contrast or dynamic range on Saturn is lower. I'll give 10FPS a shot tomorrow, but it might simply end up too noisy if I have to push the gain up some more.

A 6 minute run is a good idea. A while back, I calculated that, at my image scale, the fastest moving part of Saturn (equator/meridian) would pass one pixel in 3.5 minutes. But, in practice, since there is no great detail in that area, a longer run makes a lot of sense.

Incidently, I am also experimenting with a Microsoft HD Lifecam. It is certainly more sensitive and I can go to 15FPS. But, it seems to be lacking in contrast. It's also producing "blocky" images. Difficult to describe exactly what I mean. But, squares of 4 pixels seem to be similar, as though they are somehow reconstucted in the camera and do not bare a direct relationship to the pixels on the chip.

I'll stick with the Neximage for the moment, but will probably go for a IS camera ready for Jupiter later this year

[Kokatha man]

Hi again 26L.....the images in this thread http://stargazerslounge.com/imaging-planetary/140105-big-22-4-saturn-4-moons.html were taken with a 44% histogram at 8150mm f/l and recorded over a full 6 minutes of capture: I also use quite a lot of gamma with Saturn.....and you're correct about differences between Saturn & Jupiter re capture settings...

[King]

would a DMK allow me to image at say 10FPS?

I use 15 and if I remember correctly, the lower one is 7.

[26Left]

Thanks for all your advice and suggestions. Seeing was very good on 10th. May and I had another go at imaging Saturn. I did the following things differently:

• I'm using a x3 TV Barlow rather than EP projection. It's easier to deal with and almost no CA.
  
• I've increased the imaging run to six minutes.
  
• I've decreased the exposure time to 1/7.5s. I probably can't go much faster than that on Saturn.
  

The image on the right is the best one. f/29 gives me an image scale of 0.31 arc sec.

The two pictures were taken 39 minutes apart. It's interesting to see how the storm has moved during that time. Rather like watching the GRS on Jupiter.

These were taken with my NexImage. I'll probably get an Imaging Source camera so I can drop the exposure times ready for Jupiter later this year.

[Space Cowboy]

They are truly outstanding images! You are getting the same detail as a scope twice the size! Without doubt the best I've seen on here with a 5" aperture. My vote for POW!

[riklaunim]

These were taken with my NexImage. I'll probably get an Imaging Source camera so I can drop the exposure times ready for Jupiter later this year.

Wait for the new TIS DMK/DBK/DFK cameras to show up. Switching from NexImage to current D*M21 camera won't change the exposure times noticably as both use the same (old) CCD. The new cams are supposed to go public by the end of summer.

[step_hen]

The results you are getting with the neximage are outstanding. I had one for a short time and really struggled to get anything decent with it.

Stephen