An advice about purchasing a Newton

[Simone_DB]

Hello everybody, this is my first post here. English is not my native language, so please bear with me!

I'm fond of astronomy related disciplines since I was a little kid (I'm now 51), but my experience with telescopes is very limited: I used a small refractor and a reflector, both when I was very young. Last year, for my birthday, my wife gave me a Konusmotor 130/1000 (500mm with Barlow 2x), which I used until now. These days I made an upgrade because I'd like to make my first step into astrophotography, but I'd also like to keep making observation. So I purchased a used HEQ5 Pro Synscan mount, and I was planning to take a 150/600 f4 newton, but I have some doubts. I saw that a 200/800 f4 is a couple of hudreds € more expensive and since I also would like not to lose too much with magnification (I sometimes have my son, his and my friends, have some fun together), so I'd like to have some insights from people more experienced than me. Sort ok know what they would do if they were in my shoes. When I'm not on vacation, I use the telescope from a terrace of a small building in a polluted (light and dust) city, which is Rome, Italy.

Apart from size aspects, which I have to think about on my own, I've never took a picture from a telescope, so I'm interested in understand what the differences could be using the two tubes. Would I encounter the same difficulties?

Since my limited knowledge I could easily have missed some important informations, in this case feel free to ask.

Thank you in advance

Edited October 3, 2023 by Simone_DB

[Cosmic Geoff]

You need to think about what exactly the telescope is for.  I assume these f4 Newtonians are intended for astrophotography - for which the only difference between the 150 and the 200 will be the image scale.  The 200 will be more affected by wind and more of a load on the mount.

What exactly do you want to image? Some popular targets will be too big to fit in the field of view.  You will also need potentially expensive accessories, e.g coma corrector, guidescope.

If you can, buy the book 'Making Every Photon Count' by Steve Richards.

For visual use, I suspect f4 is less than ideal.  Likewise it is less than ideal for planetary imaging.

Trying to make 1 telescope do all things rarely works well.

If you want an easier introduction to deep sky imaging, putting a DSLR on a tracker mount is probably the way to go.  (or on the HEQ5, since you already bought it.)

Edited October 3, 2023 by Cosmic Geoff

[Simone_DB]

1 hour ago, Cosmic Geoff said:

You need to think about what exactly the telescope is for.  I assume these f4 Newtonians are intended for astrophotography - for which the only difference between the 150 and the 200 will be the image scale.  The 200 will be more affected by wind and more of a load on the mount.

What exactly do you want to image? Some popular targets will be too big to fit in the field of view.  You will also need potentially expensive accessories, e.g coma corrector, guidescope.

If you can, buy the book 'Making Every Photon Count' by Steve Richards.

For visual use, I suspect f4 is less than ideal.  Likewise it is less than ideal for planetary imaging.

Trying to make 1 telescope do all things rarely works well.

If you want an easier introduction to deep sky imaging, putting a DSLR on a tracker mount is probably the way to go.  (or on the HEQ5, since you already bought it.)

Thank you for your reply!

Yes, I'd like to make my first steps into astrophotography, in particular of deep sky objects. And the reason I opted for an f4 was for that reason. The model the dealer was suggesting me is a Newton Quattro (150/600), that is sold with a coma corrector, which also should, from what I read, take the f number to 3.45.

Since you named the DSLR, I take the chance to add something I forgot in the previous post: I could not focus properly with my reflex and the 130/1000, and I found out that the problem is typical with 150mm (and smaller) reflectors. So, I also considered the 200mm because I was sure not to encounter that problem again. Do you think I should be fine with the 150mm, anyway?

Thanks for the reminder about the wind. My terrace, as a matter of fact, is often swept by it. I'll think about that.

Also thanks for making it quite clear that I can't expect to do photography and observation and have good results on both. Speaking of this anyway, do you think a barlow lens could help, when I want to make observation, and take that off during photography sessions? Or are there any other workarounds that could make the instrument more versatile?

Thanks!

 

P.S. Thanks also for the advice about the book!

 

 

[Elp]

The focus issue with your previous scope could have something to do with the focuser, some don't have the focus travel in order to reach focus with a camera without modification, you also need to ensure you've set the correct backfocus to the camera sensor with spacers, you'd also need a coma corrector if you want to get a flat star field across the whole sensor.

Personally, I'd look at a decent doublet or triplet apo refractor, preferably with decent glass and a good rack and pinion focuser, you'll get much less hassle in getting it working well as well as it working better on a breezy night. I've owned Newtonian, SCT and refractor both acromat and apochromatic, the last one is the easiest to image with as well as getting the crispest sharpest visual views but at the cost of aperture and focal length.

Edited October 3, 2023 by Elp

[bosun21]

You could also look at the Skywatcher 150PDS which is designed for astrophotography but can comfortably do visual as well. Your existing scope is a bird jones design which isn’t really suitable for either for several reasons. The 150 PDS is a capable telescope and being a smaller diameter than the 200 won’t be so much of a wind sail. Your cameras will also be able to achieve focus. If you are considering a reflector then you will need to learn how to collimate it. If you don’t want to be bothered with having to collimate then a smaller ED doublet refractor would be the way to go.

[Cosmic Geoff]

3 hours ago, Simone_DB said:

Speaking of this anyway, do you think a barlow lens could help, when I want to make observation, and take that off during photography sessions? Or are there any other workarounds that could make the instrument more versatile?

In practice, you would be using a Barlow lens or exotic eyepieces to gain enough magnification for many visual observations.  If you are observing from a light polluted location, this will bias you toward observing small bright objects (double stars , planets, etc), for which a scope with a native long focal ratio would be more suited, e.g. a f10 SCT. 

As I hinted earlier, you should not give much weight to the idea of a versatile instrument.

[Simone_DB]

13 hours ago, Elp said:

The focus issue with your previous scope could have something to do with the focuser, some don't have the focus travel in order to reach focus with a camera without modification, you also need to ensure you've set the correct backfocus to the camera sensor with spacers, you'd also need a coma corrector if you want to get a flat star field across the whole sensor.

Personally, I'd look at a decent doublet or triplet apo refractor, preferably with decent glass and a good rack and pinion focuser, you'll get much less hassle in getting it working well as well as it working better on a breezy night. I've owned Newtonian, SCT and refractor both acromat and apochromatic, the last one is the easiest to image with as well as getting the crispest sharpest visual views but at the cost of aperture and focal length.

Hi and thanks! Yes the problem was that the camera sensor is too far from the focus point, so the solution can't be a spacer (which, by the way, I bought). From what I got, the solutions are: a barlow lens, with all the relative cons, or move the primary mirror towards the secondary, which I didn't want to do. Or, I believe, you can get rid of that with a mirrorless, which has the sensor closer to the eyepiece.

I'll think about a refractor, but I'm hesitant because I've no experience with those, and the budget is an issue 😅

[Simone_DB]

13 hours ago, bosun21 said:

You could also look at the Skywatcher 150PDS which is designed for astrophotography but can comfortably do visual as well. Your existing scope is a bird jones design which isn’t really suitable for either for several reasons. The 150 PDS is a capable telescope and being a smaller diameter than the 200 won’t be so much of a wind sail. Your cameras will also be able to achieve focus. If you are considering a reflector then you will need to learn how to collimate it. If you don’t want to be bothered with having to collimate then a smaller ED doublet refractor would be the way to go.

Thank you, the model you suggest is indeed the compromise I was asking about. As other said, a compromise is never the best solution (this was the reason I was thinking about a barlow lens that I can take off and I have the original instrument), but I asked for it, and you gave it to me, so I thank you. 🙂

[Simone_DB]

13 hours ago, Cosmic Geoff said:

In practice, you would be using a Barlow lens or exotic eyepieces to gain enough magnification for many visual observations.  If you are observing from a light polluted location, this will bias you toward observing small bright objects (double stars , planets, etc), for which a scope with a native long focal ratio would be more suited, e.g. a f10 SCT. 

As I hinted earlier, you should not give much weight to the idea of a versatile instrument.

Thank you again Cosmic Geoff, you and the others gave me precious information that helped me to better understand the situation. I'll talk with my reseller and I'll update you when I will have taken a decision!

[Elp]

2 hours ago, Simone_DB said:

think about a refractor, but I'm hesitant because I've no experience

If you get a decent one, the only real issue you'll have is setting the backspacing correctly to get a complete flat field across the sensor, once done it's either set or easy to repeat, for a DSLR most field flatteners have 55mm back spacing so it's usually simply a case of camera > t ring > onto back of flattener and done. A lot of focusers can rotate or the flattener may have a rotation section so framing is also easy. 

They do however cost more for a good one but you don't have to break the bank, both my used 60mm and 100mm were relatively cheap, in fact if I think about it, none of my scopes have cost much at all as they've all been bought used, cameras and mounts having cost more.

[bosun21]

The 150PDS will comfortably do both visual and astrophotography. A barlow could be used for visual to achieve high magnification. Good luck with whatever you decide.

[Simone_DB]

I called the reseller and after a brief exchange (in which I reported all your thoughts 🙂), we went for the 150/600 which I will operate with a good barlow for observation of bright objects (3x probably, since the telescope has a good f number).

I thank you again and I hope to post some results asap. You're all very kind and I'm, sure I'll have a nice time here! I hope you all have a nice day! 🙏

As a gift, I'll attach the only pictures I took with the 130/1000 and the smartphone. I think I'd rather NOT have a feedback about them! 😁

 

[Elp]

Perfectly fine images, Saturn is difficult to get any amount of decent definition out of at the best of times.

[Simone_DB]

8 minutes ago, Elp said:

Perfectly fine images, Saturn is difficult to get any amount of decent definition out of at the best of times.

Well, thank you sir! 🙂