sky-watcher Problem with focusing

[Simone_DB]

Hello, I've just purchased a Sky-watcher newton 150/600 that I mounted on a EHQ5 Synscan to begin to do some imaging (I've no previous experience of astrophotography). Yesterday evening I mounted my Nikon D5100 on the telescope with a T2 ring, an adaptor for a coma corrector (a few millimeters thick) and the coma corrector itself. There are no other elements in the optical train. I tried to get jupiter in focus, but I couldn't. It seemed to me that the sensor of the camera is too far away, because it seemed to get better as I moved the focuser so that the camera would get closer to the tube, but at the end of the travel, Jupiter was still out of focus.

I know that this is a typical problem of the newtons, but I've read that the issue involves tubes under 150mm. I'm aware of some workarounds which involves moving the primary mirror (which I'll never try), and the other is by using of a barlow lens. I've purchased one (2.25x) along with the tube (for observation, it's an f4), but still no luck, even if it seemed to improve.

I'm a bit frustrated and I'd like to have some insight/ideas. thanks a lot!

[bosun21]

3 minutes ago, Simone_DB said:

Hello, I've just purchased a Sky-watcher newton 150/600 that I mounted on a EHQ5 Synscan to begin to do some imaging (I've no previous experience of astrophotography). Yesterday evening I mounted my Nikon D5100 on the telescope with a T2 ring, an adaptor for a coma corrector (a few millimeters thick) and the coma corrector itself. There are no other elements in the optical train. I tried to get jupiter in focus, but I couldn't. It seemed to me that the sensor of the camera is too far away, because it seemed to get better as I moved the focuser so that the camera would get closer to the tube, but at the end of the travel, Jupiter was still out of focus.

I know that this is a typical problem of the newtons, but I've read that the issue involves tubes under 150mm. I'm aware of some workarounds which involves moving the primary mirror (which I'll never try), and the other is by using of a barlow lens. I've purchased one (2.25x) along with the tube (for observation, it's an f4), but still no luck, even if it seemed to improve.

I'm a bit frustrated and I'd like to have some insight/ideas. thanks a lot!

You don’t need a coma corrector for planetary as you are only capturing the planet on axis. Remove it and try again. What model of scope is it?

[Simone_DB]

1 hour ago, bosun21 said:

You don’t need a coma corrector for planetary as you are only capturing the planet on axis. Remove it and try again. What model of scope is it?

Hi Bosun21, thanks for your reply. This is the telescope I bought. I'll try again without the coma corrector as soon as I can, but I'm not sure how it could affect the focus issue. Does it change the focal length of the optical train substantially?

Thanks again for your time

[bosun21]

5 minutes ago, Simone_DB said:

Hi Bosun21, thanks for your reply. This is the telescope I bought. I'll try again without the coma corrector as soon as I can, but I'm not sure how it could affect the focus issue. Does it change the focal length of the optical train substantially?

Thanks again for your time

Looking at your scope you should be able to achieve focus as the Quattro is designed for it. It may be the distance between the coma corrector and the sensor that is incorrect. Edit the title with the addition of Quattro added and someone who owns one can put you right. Good luck.

[Simone_DB]

Thanks! I added a tag to the title, but I couldn't edit the title itself 🙁

I'll attach an image of the camera mounted when possible!

The coma corrector has the shape of this one below:

Edited October 20, 2023 by Simone_DB

[uhb1966]

i have a skywatcher f4 200/800. in my case, i need to mount an extension as the fokus point is farther away from the scope. 

Edited October 24, 2023 by uhb1966

[Simone_DB]

11 hours ago, uhb1966 said:

i have a skywatcher f4 200/800. in my case, i need to mount an extension as the fokus point is farther away from the scope. 

Hi, thanks for your reply. I have this extension that I had previously bought for a 130mm I was using before this one (by the way, I bought it erroneously because it worsened the problem), but it's a 1.25", so I don't think I can use it. In any case what I don't get is the fact that wherever I read things on the subject, it seems that the problem is that Newtons have the focus point too close to the tube. Now you are saying that you had to move your camera back. Frankly I'm perplexed*.

Anyway I tried just once, so maybe I made some mistake, even if I don't know which, since I only had the camera in direct focus with the T2 ring and an adapter. I should be fine with my equipment. I'll try again as soon as clouds allow me, we got bad weather these days.

Thanks again!

*I'm perplexed also for your case since I read that the focus issue concerns newtons under 150mm.

Edit: I found an interesting article which describe my problem. In particular the section "The solution – a Barlow lens", because I've done just what he describes, that is, I've used it but maybe not the right one (see "You have to use the right Barlow").

I'll let you know. In the meanwhile if someone has a clear idea on the topic, I'm more than eager to hear from them

 

Edited October 25, 2023 by Simone_DB

[AstroMuni]

44 minutes ago, Simone_DB said:

wherever I read things on the subject, it seems that the problem is that Newtons have the focus point too close to the tube. Now you are saying that you had to move your camera back. Frankly I'm perplexed*.

What you have read is a generic problem. The SW Quattro, PDS series have been specially designed to get around this problem and have shorter distances between primary and the focuser tube.

[alacant]

On 20/10/2023 at 14:13, Simone_DB said:

image of the camera mounted when possible!

Hi

Any progress on this? 

You don't need clear skies to check focus. Point at e.g. a distant tree with the camera set to live view. 

The quattro will reach focus easily, even with a dSLR,  always supposing you have the shoulder of the cc 55mm from the sensor. A m48 to Eos adapter, 11mm thick, is all you need. No other adapter or extension is required.

Cheers 

Edited October 26, 2023 by alacant

[uhb1966]

+1 for astromuni and alacant.

[Simone_DB]

20 hours ago, AstroMuni said:

What you have read is a generic problem. The SW Quattro, PDS series have been specially designed to get around this problem and have shorter distances between primary and the focuser tube.

Hi thanks. Yes, I also think I should have no too  much trouble in focusing. And in fact I think my issues are more related to the fact that...I have to learn to take astro pictures! Yesterday I stayed out for about an hour and...(see below)

[Simone_DB]

16 hours ago, alacant said:

Hi

Any progress on this? 

You don't need clear skies to check focus. Point at e.g. a distant tree with the camera set to live view. 

The quattro will reach focus easily, even with a dSLR,  always supposing you have the shoulder of the cc 55mm from the sensor. A m48 to Eos adapter with a thickness of 11mm thick is all you need. No other adapter or extension is required.

Cheers 

As I was saying, yesterday I took a couple of pictures. It was a short session mainly for the clouds. It was mostly covered or scattered, so I couldn't align the scope and went completely manual. The following pictures show the equipment and the mounted camera with and without barlow.

The daylight picture was taken to check the focus as suggested, and it seems quite right (I think). The trget is about 4-500m away. The other ones show Jupiter with and without a barlow (the best ones 😔). And the open cluster (if it is), I think it's the Pleiads. I attached one where trails can be seen (I think it was 2 secs exposure), while the others are about 1 sec exp.

The Jupiter best one, where you can barely see the two cloud belts is underexposed for the satellites, while the inthe others you can see the sats, but Jupiter is too bright.

All the pictures a unedited RAW, then converted to JPG and downsized to 1280x1024.

I think I need some suggestions about exposure and ISO (I think I cannot set anything else on direct focus) both for planets and stars and any comment is appreciated! 🙂

The open cluster was taken with NR on long exposure even if it wasn't that long.

I'll try again when I'll be able to properly align the scope.

Tanks for your time!

Edited October 26, 2023 by Simone_DB

[Simone_DB]

Here is a crop of the best Jupiter

[alacant]

On 20/10/2023 at 11:50, Simone_DB said:

an adaptor for a coma corrector (a few millimeters thick)

The spacing is CRITICAL. The coma corrector has a m48 thread. So...

Lose the Barlow and the t2 adapters.
To set the correct spacing, all you need is the Nikon version of one of these. Keep it simple!

https://www.amazon.es/Vbestlife-Adaptador-Aluminio-Adaptarse-M48-EOS/dp/B07PP26BGD/ref=sr_1_2_sspa?adgrpid=123572583348&hvadid=486013403758&hvdev=c&hvlocphy=20267&hvnetw=g&hvqmt=e&hvrand=2999691609468659050&hvtargid=kwd-343260146324&hydadcr=13173_1805824&keywords=canon%2Bm48&qid=1698314569&sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

Cheers and HTH

Edited October 26, 2023 by alacant

[Denys]

Hi there,

I am by no means an expert, but I've heard people saying that a good way to know if you are on focus with a dslr is to point at Jupiter, and when you can see its four moons you should be on focus (or at least very close to)... And from your images, it looks like you are there.

Since you mentioned you should learn how to take astrophotos, here is a very helpful tutorial (IMO) for planetary images with a dslr:

 

HTH,

Denys

[Simone_DB]

@alacant thanks a lot! If I remember correctly, the reseller gave me the adaptor because he already sold the T ring to me (for a 130mm I previously had). But since it's something cheap, I'll consider the purchase. Thank you!

@Denys Yes, I used the satellites to check the focus, I'm glad I got it right. I'll check the video as soon as I can, thank you!

Edited October 26, 2023 by Simone_DB

[AstroMuni]

6 hours ago, Simone_DB said:

Yesterday I stayed out for about an hour and...(see below)

Thats a good start and the moons of Jupiter are showing quite clearly in one of the images. You will need to take a video and stack the images to bring out the bands etc. You have jumped the main hurdle of getting a good focus. 🙂 Make sure your mount is Polar aligned so that tracking will be smooth and you dont end up getting star trails. The HEQ5 is a very capable mount.

Good luck.

Edited October 26, 2023 by AstroMuni

[Simone_DB]

1 hour ago, AstroMuni said:

Thats a good start and the moons of Jupiter are showing quite clearly in one of the images. You will need to take a video and stack the images to bring out the bands etc. You have jumped the main hurdle of getting a good focus. 🙂 Make sure your mount is Polar aligned so that tracking will be smooth and you dont end up getting star trails. The HEQ5 is a very capable mount.

Good luck.

Astromuni, thank you! 🙂Can I take a video with the camera itself and then process it with some software? Do you recommend any in particular? I saw the video that @Denys linked and I wasn't able (yet) to grasp a lot about the programs the guy uses, of course. But if you or someone else is willing to suggest what sw should I begin to get to know is welcome, since I have no experience and I guess there are many of them.

Edited October 26, 2023 by Simone_DB

[Denys]

Hi again,

There are lots of people here in SGL who are very knowledgeable on this, so perhaps they can give you better answers or even some workflow to follow so you can start making your imaging... But here are some things that I think are relevant (perhaps you know this already):

1. In summary, there are two different types of workflow in astrophotography: it depends if you are imaging a Deep Sky Object (DSO) or a planet (include moon here as well)...

2. For DSO, you (usually) want photos with long exposure - because the objects are very dim. For this, you need to be polar aligned.

3. For planetary imaging, you want to make a short video (you'll find that the video cannot be too long because of the rotation of the planets) - but a couple of minutes is a good start. Here, the faster the frame rate of your video, the better (see topic 5). Why a video? Because in this case a long exposure picture will be very blurry due to turbulence in the atmosphere. Thus you make a single video, and then break the video file into its individual frames, select those frames that are less blurry, stack them together into a single picture, and finally apply some tools to reduce noise and increase the sharpness of your image...

4. As you might have noticed, there are lots of different software out there, but the most common workflow that I've seen involves using three of them in combination (since each one does a different job): PiPP, Autostakkert, and RegiStax 6.

5. You will see that people often recommend a dedicated astrocamera for planetary imaging since DSLRs are not very suited for this task. This doesn't mean it cannot be done, and that's what I wanted to show you in the video that I linked above. Mind you, the video I linked before wasn't indeed the best tutorial out there to learn your way into the software (but I do recommend that channel for DSO, I have found it really good in walking you through all the steps from imaging to processing).

6. Here is another video that I've found helpful for planetary processing - very short video, so do not expect an in-deepth analysis of what the software can do, but it does explain a little better what each one it is doing and perhaps will give you a place to start:

https://www.youtube.com/watch?v=Ha1BDVkl70I

HTH,

Denys

[Simone_DB]

13 hours ago, Denys said:

Hi again,

There are lots of people here in SGL who are very knowledgeable on this, so perhaps they can give you better answers or even some workflow to follow so you can start making your imaging... But here are some things that I think are relevant (perhaps you know this already):

1. In summary, there are two different types of workflow in astrophotography: it depends if you are imaging a Deep Sky Object (DSO) or a planet (include moon here as well)...

2. For DSO, you (usually) want photos with long exposure - because the objects are very dim. For this, you need to be polar aligned.

3. For planetary imaging, you want to make a short video (you'll find that the video cannot be too long because of the rotation of the planets) - but a couple of minutes is a good start. Here, the faster the frame rate of your video, the better (see topic 5). Why a video? Because in this case a long exposure picture will be very blurry due to turbulence in the atmosphere. Thus you make a single video, and then break the video file into its individual frames, select those frames that are less blurry, stack them together into a single picture, and finally apply some tools to reduce noise and increase the sharpness of your image...

4. As you might have noticed, there are lots of different software out there, but the most common workflow that I've seen involves using three of them in combination (since each one does a different job): PiPP, Autostakkert, and RegiStax 6.

5. You will see that people often recommend a dedicated astrocamera for planetary imaging since DSLRs are not very suited for this task. This doesn't mean it cannot be done, and that's what I wanted to show you in the video that I linked above. Mind you, the video I linked before wasn't indeed the best tutorial out there to learn your way into the software (but I do recommend that channel for DSO, I have found it really good in walking you through all the steps from imaging to processing).

6. Here is another video that I've found helpful for planetary processing - very short video, so do not expect an in-deepth analysis of what the software can do, but it does explain a little better what each one it is doing and perhaps will give you a place to start:

https://www.youtube.com/watch?v=Ha1BDVkl70I

HTH,

Denys

Denys thank you so much, a general idea of the workflow for the different types of objects is exactly what I was looking for! I'll check that channel for sure and also the video you linked asap. I just hope that the weather will improve a bit the next days, but looking at the forecast, it could be take a while.

Also I stumbled upon a couple of articles regarding camera modding, but all I know so is that such a thing exists, more or less. I'll dig into it as well!

Again, I really thank you, such a concise and accurate post is extremely useful to me!  If you PM me your address I can send you some good italian wine. ☺️

I hope I can post some results soon! Have a nice day everyone!

Edit: I saw the video, fantastic! 👌

Edited October 27, 2023 by Simone_DB

[Denys]

Hi Simone,

I'm really glad that I was able to assist you. When I was just starting out with astrophotography, the support I received from everyone in this forum was invaluable. It's incredible to now be in a position where I can offer help to others who are embarking on this same journey.

I appreciate your offer, but there's really no need for the wine. Trust me, as you delve deeper into astrophotography, you'll discover a never-ending list of equipment that you'll want to invest in, so it's best to save your money for those occasions!

Regarding modding the camera, all I know is that it involves removing the infra-red filter that is in front of the sensor. I have a canon which I use for my astrophotography, but I never had it modified – but people often say that it can really boost your images of DSO, since (depending on the object) a lot of the signal is actually in that part of the spectrum.

Good luck with everything!

Best regards,

Denys

[Cosmic Geoff]

Two books: "Making Every Photon Count" by Steve Richards (for deep sky imaging) and "Guide to High Resolution Lunar and Planet Imaging" by Dave Eagle.  The former is available from FLO.

[Simone_DB]

1 hour ago, Cosmic Geoff said:

Two books: "Making Every Photon Count" by Steve Richards (for deep sky imaging) and "Guide to High Resolution Lunar and Planet Imaging" by Dave Eagle.  The former is available from FLO.

Good to know Cosmic Geoff, thanks a lot!😉

Edited October 27, 2023 by Simone_DB

[Simone_DB]

3 hours ago, Denys said:

Hi Simone,

I'm really glad that I was able to assist you. When I was just starting out with astrophotography, the support I received from everyone in this forum was invaluable. It's incredible to now be in a position where I can offer help to others who are embarking on this same journey.

I appreciate your offer, but there's really no need for the wine. Trust me, as you delve deeper into astrophotography, you'll discover a never-ending list of equipment that you'll want to invest in, so it's best to save your money for those occasions!

Regarding modding the camera, all I know is that it involves removing the infra-red filter that is in front of the sensor. I have a canon which I use for my astrophotography, but I never had it modified – but people often say that it can really boost your images of DSO, since (depending on the object) a lot of the signal is actually in that part of the spectrum.

Good luck with everything!

Best regards,

Denys

Hi Denys, yes, you and the others already gave me a great support. It's not always easy to find a forum where people, for various reasons, get to understand what you need or sometimes they just have a kind of aggressive or dismissive attitude. I'm glad I found such a kind and welcoming environment here. I'd be more than willing myself to help other people one day.

About the modding of the camera, I have a collegue that own a Nikon D3100 which he removed the IR filter from, and he's not using it anymore, so I'll have a chance to make some practice with that! Buy the way, such a modding is suitable just for reddish objects, or is it good in general for DSOs?

Edit: I just reread your last post and I noticed that you already answered, at least partially, to my question. Thanks!

Edited October 27, 2023 by Simone_DB

[Denys]

2 hours ago, Simone_DB said:

Hi Denys, yes, you and the others already gave me a great support. It's not always easy to find a forum where people, for various reasons, get to understand what you need or sometimes they just have a kind of aggressive or dismissive attitude. I'm glad I found such a kind and welcoming environment here. I'd be more than willing myself to help other people one day.

About the modding of the camera, I have a collegue that own a Nikon D3100 which he removed the IR filter from, and he's not using it anymore, so I'll have a chance to make some practice with that! Buy the way, such a modding is suitable just for reddish objects, or is it good in general for DSOs?

Edit: I just reread your last post and I noticed that you already answered, at least partially, to my question. Thanks!

Oh, it's great that you can get the chance to try a modified camera. What is even better is that you can compare both cameras and check for yourself whether or not it is worth it.

Like I said, I have no experience with a modded DSLR, but if I had to make a wild guess I would say that it will give you better results for most DSOs. But you touch an interesting point about the reddish objects. For instance, I was checking for some pictures of Orion with modified DSLRs on astrobin and most of the images have a very strong reddish color (which I have to say, it’s not of my personal liking - but perhaps that can be treated in post-processing?). On the other hand, I once tried to capture the flame + horsehead nebula or the Rosetta nebula and didn’t have much of a success, and I think it’s probably due to the IR filter that is blocking most of the signal in these specific targets.

Anyhow, please let me know your thoughts on this once you get the chance to try the cameras.

Regards,

Denys