Celestron 8se and ZWO ASI 183MC Pro - Day 1 - disastrous start - help please

[Meluhanz]

I have been using Celestron nexstar 8se for a little while and I enjoy viewing the planets and few constellations.  I enjoyed the view that I wanted to capture them. Tried connecting my very old DSLR (Canon eos 600D), but capture very faint objects and i noticed there was focus issue, blamed it on the DSLR and bought a ASI 183MC pro (on marketPlace - impulsive shopping).

Now, the videos and online forums i see that the camera is directly connected to the telescope, but this ASI did not have a connector that gets to the telescope, I could use part of the dslr's t connector to make it fit like below:

 

First problem: Though I can see the planets/stars clearly through the lens, when I replace it with camera, it totally out of focus. In this case, the Jupiter which was clearly visible with its moons appeared like this - 

 

I did kept adjusting the focuser turning it for every pic until I got something decent 

 

Finally

 

 

What am I doing wrong here? I was expecting the astro camera to capture what I see through the lense, maybe more.   

 

 

 

 

[ollypenrice]

The focal plane of an eyepiece is a very long way from the focal plane of the camera so refocus is always needed. There is a device called a flip mirror which lets you flip between EP and camera with both in focus.

You should not be using a diagonal, either, with a camera. You need a camera adapter which will screw into the back of the SCT. Fortunately these scopes have a huge range of focus so you may not need anything else. Sometimes an extension tube is needed to place the camera further from the objective.

[michael8554]

1. The telescope forms an image beyond the rear of the tube.

That position is varied by the focuser.

The lenses/eyepieces give different "magnification" depending on their focal length, usually engraved on the eyepiece.

For example, a 10mm eyepiece will "magnify" more than a 25mm eyepiece.

"Tried connecting my very old DSLR (Canon eos 600D), but capture very faint objects and i noticed there was focus issue"

Your 600D is an excellent camera to start with, and is often used with these telescopes.

You have to attach it with only enough adapters to allow the sensor to be positioned within the range of focus that the telescope provides.

And faint objects require long exposures, minutes not seconds.

With your Jupiter shot you got to focus in the end.

You will now appreciate that the telescope focuser has a very large range of adjustment, many many turns of the knob.

The image is over-exposed, so reduce the exposure.

Switch to the Manual setting and adjust the shutter speed to a faster setting.

2. The ASI 183MC Pro is versatile, so can be used for Planetary and Deep Sky DSO imaging.

But its small pixels 2.4um are not a good match to the telescope for DSO imaging.

Michael

 

[Elp]

There's two branches to go down when doing this:

1. Do you want to image planets only?

2. Do you want to image DSOs too?

If it's (1), then the camera you've got isn't ideal. It can be done but it's a large resolution camera, even if you have a small region of interest defined (cropped resolution for imaging planets), you might find the frames per second aren't too fast for capturing planets (look up planetary imaging, it's done by taking hundreds of thousands of images within the space of a few minutes, then post processed to eliminate the frames which are blurry due to atmospheric seeing and stacking the good frames). You dont have to do the specific planetary imaging routine and can capture singular images but you'd have to take a fair few then choose the best out of them when seeing was better (seeing is changing constantly, think of when you look through warm air say above hot roads and how the background shimmers). As mentioned above it's better to fit the camera straight through in line with the optics rather than via a diagonal. But you'll need some extension pieces, maybe longer than 60-100mm or more to fit between the visual back and the camera.

If it's (2), in the default f10 configuration the speed of the scope isn't ideal although you have a good aperture size which mitigates the speed issue, the default mount you have moves in altitude (up down) and azimuth (left right), also referred to as alt-az, this also isn't ideal for imaging dso as equatorial mounts are better designed for the task of keeping targets centred (which you need when doing long exposure imaging of faint targets) and moving and counteracting the earth's rotation. So you need to speed the system up with celestrons F6.3 reducer. With this you unscrew the visual back from the back of the scope, screw on the reducer, then screw on extension pieces then the camera. I'm not sure of the C8s backfocus distance (distance from a reducer lens to camera sensor for the image plane to be able to get into focus once the scope is focused) but on my C6 this measurement is around 105mm, can be up to 120mm (SCT backfocus distance is a lot more forgiving than a refractor/newtonian telescope). With this setup you'll be able to capture fairly bright DSO targets quite easily as single images, they'll look better than how you see them visually, but may need slight post processing to bring out further detail. Proper astrophotography requires hundreds or thousands of images to be stacked to accumulate all that faint light from space. But taking images with this setup is still possible with few exposures, people also use this for EAA where a camera is acting like the eyepiece and the software live stacks the images enhancing the image per capture in real time.

Edited December 29, 2023 by Elp

[bwj]

Take a look at this article. A lot of good information specifically for the 8SE. with both a dslr and astro camera.

https://www.sdfalchetti.com/blog-1/2021/1/16/astrophotography-with-the-nexstar-8se

Clear skies!

Edited December 29, 2023 by bwj
correct typo

[Paul2019]

Looks like you managed to get focus eventually! I’ll leave the diagonal conversation to others that know better than I, but I think you over exposed when you got focus. 
 

I’ve only used my ASI183mm pro on Jupiter to get somewhat focused to PA but I know that I had to use video mode and very short exposures <50ms to actually get a view, maybe that will help with your conundrum? 
 

HTH 

 

Paul

[ollypenrice]

Regarding the imaging of the deep sky with this setup, I would not invest in any accessories to make this possible because the scope and mount are fundamentally unsuitable and will remain so. Like many other people I set about converting my alt-az SCT for deep sky imaging, spent a lot of money and never took a presentable picture with it.

Regarding planets, note that 'cropped resolution for imaging planets' does not alter the resolution in any way, though it will probably allow you to run a faster frame rate.

Olly

Edited December 30, 2023 by ollypenrice
False click

[Priesters]

Only thing I’d add is that if you do swap things around (e.g. remove diagonal and use extension tubes) you’ll need to refocus.  My advice is to try and get rough focus during the daytime on the most distant object you can see.  It makes life so much easier and quicker when you are in the dark searching for a tiny object in the sky.

[Cosmic Geoff]

I have a C8 SE and can confirm that while it is a good instrument for visual observing, it is a pain to use for planetary imaging and totally unsuitable for deep space imaging.  And yes, you do have to do a major re-focus when swapping an eyepiece for a camera.

That big camera on the end of a slim diagonal and visual back looks like an accident waiting to happen. 

My advice: if you want to do planetary imaging, trade the C8 SE for  CPC800, or get a HEQ5 mount to re-mount your C8 OTA. You may also need a more suitable camera, depending on the ASI183MC's spec.

If you want to do deep space imaging, buy some totally different kit, depending on what sort of object you want to image, as deep space targets vary widely in size from many degrees to a few minutes of arc.   The popular 'small refractor'  is mainly suited to mid-sized targets.

[Meluhanz]

Thank you all for responding. Learning focal length the hard way. I got a adapter so I can connect the camera directly to the SCT, but as mentioned above, the telescope does not seem to be a great fit. The telescope view is soo zoomed in that I cannot get a good field of view for the camera. 

Well, before i give up on it, i've ordered a focal length reducer/corrector. 

My plan B is to revive the old Orion Starmax 102mm equatorial telescope and try my ASI camera with it.  

[Meluhanz]

On 29/12/2023 at 03:05, michael8554 said:

d connecting my very old DSLR (Canon eos 600D), but capture very faint objects and i noticed there was focus issue"

Your 600D is an excellent camera to start with, and is often used with these telescopes.

You have to attach it with

 

23 hours ago, ollypenrice said:

Regarding the imaging of the deep sky with this setup, I would not invest in any accessories to make this possible because the scope and mount are fundamentally unsuitable and will remain so. Like many other people I set about converting my alt-az SCT for deep sky imaging, spent a lot of money and never took a presentable picture with it.

Regarding planets, note that 'cropped resolution for imaging planets' does not alter the resolution in any way, though it will probably allow you to run a faster frame rate.

Olly

This is kind of heart breaking. My amateur brain was bigger telescope, better for viewing and better for photos

[ollypenrice]

55 minutes ago, Meluhanz said:

 

This is kind of heart breaking. My amateur brain was bigger telescope, better for viewing and better for photos

I'm sorry and many hearts have been broken in exactly this way. Your big telescope is certainly better for viewing so that's OK, and it can image the planets well. A dozen years ago the intensive marketing of SCTs by Meade and Celestron caught out lots of newcomers wanting to image the deep sky. It's not impossible to do so but a look on the forums at what people actually use will tell you all you need to know. At moderate prices the favourites are Newts or small refractors - and by a mile.

You will also read, again and again, that the first priority is neither scope nor camera but mount. This is repeated quite simply because it is true. If you try to shoot a photo with a £12,000 Hassleblad held at arm's length while riding a unicycle, you would get a better result from a Box Brownie held properly while standing on the ground. The sky moves and the scope must move with it, with a precision of about one part in two million. Incredibly, this is possible on amateur budgets.

So much is counter intuitive in AP that exhaustive homework is a must before writing any cheques. Or rather, before writing any other than this one: https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

Olly

[Priesters]

Whilst I totally agree with the advice given on telescope/camera set up for DSO imaging it’s perhaps not such a lost  cause as you may think.  If you are willing to invest further in a tracking equatorial mount you may find you can get some acceptable images of the smaller DSO’s (distant galaxies and planetary nebula).  You will need to use ‘binning’ to get a sensible pixel scale though. Investment in a decent mount will also not be wasted if you change scope/camera at a later date.  At the risk of putting my head over the parapet I’ve added a couple of examples from my 8” SCT with reducer and camera with APS-C sensor that has 3.75 um pixels @ 2xbinning. They’ve been post processed using SIRIL which is free software and Topaz AI which isn’t free.  However, as people have already said, I’d think very hard before spending more on your current set up unless it’s something transferable to another set up at a later date.

Please be gentle people, we all have different views on what’s an acceptable image and I’m only posting this because the OP already has the SCT, camera and reducer and investment in a decent mount would not be wasted if he went a different route in the future.

 

Edited December 31, 2023 by Priesters

[johnturley]

On 29/12/2023 at 08:24, Meluhanz said:

 

Finally

What am I doing wrong here? I was expecting the astro camera to capture what I see through the lense, maybe more.   

 

To me it looks like the gain has been set too high, i.e. Jupiter is overexposed and the brightness of the image has swamped out any surface detail that might be visible. 

What imaging program are you using, I use Sharpcap which is available for free download, and I prefer it to the ZWO ASI software.

John 

Edited December 31, 2023 by johnturley

[Meluhanz]

 

 

So, here is another attempted setup to get some pictures of Orion and/or Andromeda. 

 

- Orion StarMax 102mm with Celestron F/6.3 Reducer Corrector

- using ZWO ASI 183MC Pro

- mounted on Star Adventurer 2i Pro

 

Open to any advice or suggestion while I wait for clear skies.

 

Edited January 3 by Meluhanz

[Cosmic Geoff]

The Celestron f6.3 focal reducer is specifically intended for f10 SCTs, and may not work so well with a Maksutov.  See this thread here:

Skymax 127 Maksutov-Cassegrain with Focal Reducer - Cats & Casses - Cloudy Nights

"Try with what you've got" is a good policy, but you may get better results with a small imaging refractor.

[Meluhanz]

11 minutes ago, Cosmic Geoff said:

The Celestron f6.3 focal reducer is specifically intended for f10 SCTs, and may not work so well with a Maksutov.  See this thread here:

Skymax 127 Maksutov-Cassegrain with Focal Reducer - Cats & Casses - Cloudy Nights

"Try with what you've got" is a good policy, but you may get better results with a small imaging refractor.

oh ooh!

[ollypenrice]

The Star Adventurer is a light, portable mount intended to carry cameras and lenses.  Even if your reducer works, your focal length will be about 800mm, a thoroughly telescopic focal length requiring a thoroughly telescopic mount. Why not buy a used prime focus camera lens, an adapter to fit your camera, and try that on the Star Adventurer.? You cannot expect it to track at 800mm, unguided. My £6000 Mesu mount could not do that.

Olly

[Meluhanz]

1 hour ago, ollypenrice said:

The Star Adventurer is a light, portable mount intended to carry cameras and lenses.  Even if your reducer works, your focal length will be about 800mm, a thoroughly telescopic focal length requiring a thoroughly telescopic mount. Why not buy a used prime focus camera lens, an adapter to fit your camera, and try that on the Star Adventurer.? You cannot expect it to track at 800mm, unguided. My £6000 Mesu mount could not do that.

Olly

I soo want to use the ASI 183 camera that i bought.

The Star Adventurer Pro manual read that a max payload of 11 pounds, so my thought was it can load even my Nexstar 8SE to try it out along with the Orion StarMax 102mm.

My last resort will be to use my Canon EOS 600D with my 18-55mm lens

[Elp]

Your difficulty is not the imaging train weight (which does factor into it depending on the mount), it's the focal length. As an example with your camera, use the least zoom and move it around from a centre point, now use max zoom and do the same and see how much more difference the slightest movement makes in how much the FOV shifts. The longer focal length in imaging the better micro movements your mount needs to be capable of, and usually requires the input from a guide camera through a guidescope to review what it's seeing and send the data through for controlling software to interpret and send movement commands to the mount (autoguiding).

I was going to suggest try a camera lens coupled to the camera with a ZWO lens adaptor but I don't think the lens you have will be good enough, most camera lenses are poor for astro. Fixed manual primes usually fare better, even vintage ones. Just try it, you may be surprised what you can achieve with them, and is always a better way to start in AP than through a telescope.

[ollypenrice]

7 hours ago, Meluhanz said:

I soo want to use the ASI 183 camera that i bought.

The Star Adventurer Pro manual read that a max payload of 11 pounds, so my thought was it can load even my Nexstar 8SE to try it out along with the Orion StarMax 102mm.

My last resort will be to use my Canon EOS 600D with my 18-55mm lens

Unfortunately the 'go to' priority in internet mount discussions tends to be payload. It shouldn't be, the priority should be accuracy. This is what underlies Elp's post above.

To understand this you need to understand the following; an imaging system has a resolution defined by how many arcseconds of sky it places on one pixel. Plenty of online calculators will give you this;

https://astronomy.tools/calculators/ccd  

You can increase resolution either by using a longer focal length or smaller pixels. The unit is arcsecs per pixel ("PP) *  The instability of the atmosphere (the 'seeing') usually means that going below 1"PP is a waste of time.

Because pixels are getting smaller this limit is reached at increasingly short focal lengths.

Now for what this has to do with your mount: in order to capture the resolution of the system in the real world, your mount needs to track with an error about half as large as your pixel scale. That is going to require a very small error. If your image system is working at 2"PP you need to track at no more than 1"PP error. The native error of an unguided mount like the EQ6 is between 20 and 30 times more than that. Ouch! That is why we use autoguiders. These will bring an EQ6 down to an error of between 0.5 and 1"PP.

If you image at a scale finer than your mount's accuracy will allow, you might as well image with a shorter focal length. You will capture the same details and have a wider field of view. The Star Adventurer is designed for low resolution imaging. You may be within its payload but you are vastly beyond its tracking precision.

Olly

* In casual daytime photography discussions 'resolution' is often used with sloppy inaccuracy to mean pixel count on the chip. This is nonsense.

 

Edited January 4 by ollypenrice
False click

[Meluhanz]

There is plenty to learn. Frankly, all the reading did not teach me what I learnt in last ~7days.  Focal length, pixels, back focus, FOV, .......

My first ever amateurish picture of M43 with all mismatched tool set, I know it is far from perfect but was happy to see this come to life.

[ollypenrice]

8 hours ago, Meluhanz said:

There is plenty to learn. Frankly, all the reading did not teach me what I learnt in last ~7days.  Focal length, pixels, back focus, FOV, .......

My first ever amateurish picture of M43 with all mismatched tool set, I know it is far from perfect but was happy to see this come to life.

Watching those first images come in is truly amazing.

Olly