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best focal length for beginner?

beginner astrophotography equipment
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#1 eddykhan993

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Posted 08 July 2020 - 06:11 PM

Hi everyone. thanks to everyones input and advice i have decided to save up for a Skywatcher EQ5 Pro Mount but the optical tube i have my eye on says focal length of f5 (600mm) i just want advice on if this is a good set up or what may be better? thanks!!

#2 eddykhan993

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Posted 08 July 2020 - 06:15 PM

skywatcher star travel 120 by the way. I realise I didn't put what optical tube

#3 TXDigiSLR

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Posted 08 July 2020 - 06:15 PM

I think we need a lot more info before we can tell you if we think it's a good set up.  What kind of Scope?  I think 600mm focal length at f5 is a good focal length to start at, but is the scope good for imaging?  Are you going to need a field flattener ?    Is it an APO / ED / Doublet, Triplet, or just an Achromat?


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#4 eddykhan993

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Posted 08 July 2020 - 06:17 PM

I think we need a lot more info before we can tell you if we think it's a good set up. What kind of Scope? I think 600mm focal length at f5 is a good focal length to start at, but is the scope good for imaging? Are you going to need a field flattener ? Is it an APO / ED / Doublet, Triplet, or just an Achromat?


its skywatcher star travel 120. I hope this helps. this is what I'm trying to find out. thanks.

#5 TXDigiSLR

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Posted 08 July 2020 - 06:19 PM

I see you added the Scope while I was replying...

 

IMO (and I'm still new to this...)    You are going to want a better scope for imaging.   The single speed focuser is a huge drawback to start.  



#6 nimitz69

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Posted 08 July 2020 - 06:45 PM

The classic advise is an 80mm class APO triplet with a robust 2.5” R&P focuser that won’t slip under the weight of a camera and all the other stuff (EFW, AF) you may add in the future. WO & Stellavue make higher end scopes but ES and even Orion’s small, fast refractors would work while you learn AP.
Learning AP is different then doing AP so this equipment will not likely be your last purchase. Buying a single scope for life rarely works with AP ...

Edited by nimitz69, 08 July 2020 - 06:47 PM.

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#7 klaussius

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Posted 08 July 2020 - 06:51 PM

I started with the NEQ5 and an 80/400 achromat. Similar to the ST 120 but shorter.

 

The longer FL of the ST will make things harder, but it's at a mid point, so maybe not too hard. I'd say you'll still be able to learn a lot with it. The EQ5 should be able to manage 1-minute unguided subs at that FL without too many bad subs.

 

I'd say go for it.

 

You will need a flattener, but I wouldn't worry about that just yet. You'll probably want a better tube when you get serious about it. For now, the ST120 will be fun to play with, and the field curvature isn't an impedement at all.

 

Expect a ton of CA though.

 

What camera are you planning to use with this?



#8 Ryou

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Posted 08 July 2020 - 07:00 PM

Personally I think that 600mm is a bit too tight to begin with. That isn't to say it won't work, however you are going to put just that much more "stress" on the other things like guiding, polar alignment, etc. It is still fairly doable depending on things, just be warned that you may have some frustration at the beginning due to it being tighter. I also believe that in general the achromatic scopes are a bit more suited for visual than imaging.

 

It's a bit more when you add on a field flattener, however I would suggest looking at something like the Zenithstar 61. At f/5.9 it's fairly average speed wise, however the FoV and focal length at 360mm is going to be more forgiving.

 

If you can find it I also am very partial to the Cat series from William Optics as a starter scope. 250mm f/4.9 is a great beginner friendly speed and focal length, plus it comes with a built in field flattener and uses a more standard camera lens style focuser if you're used to that already. 250mm is actually very wide, however even with an APS-C DSLR is not so wide you can't get some detail and capture the larger DSO in a single frame vs a mosiac. It's also going to be the most forgiving on the guiding and polar alignment and the like too.

 

All that said, this does assume you do not already have that scope. If you do then definitely use that. Don't be afraid to try what you have already to see if this is for you and where the shortcomings may be to get that taken care of next. For example to kind of build on what klaussius said, if the corner stars are being elongated too much and bugging you then maybe it's time to look at the field flattener (if you don't have it already). You'll still get experience in setting up, taking down, etc in the meantime though which can be very valuable.



#9 klaussius

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Posted 08 July 2020 - 07:17 PM

Oh, that's right. Sorry. I missed this crucial fact:

 

Hi everyone. thanks to everyones input and advice i have decided to save up for a Skywatcher EQ5 Pro Mount but the optical tube i have my eye on says focal length of f5 (600mm) i just want advice on if this is a good set up or what may be better? thanks!!

I guess the emphasized part implies he hasn't bought it yet. So, what Ryou said, if imaging is your goal, that's not an ideal scope. An 80mm F5 tube is a far better starter option. Easier to handle so easier to learn, and a great FL for many nice bright targets. If your budget allows for an APO or an ED doublet, go for that instead of an achromat. These scopes will provide much better image quality, and they tend to be better mechanically as well, and you'll never really outgrow them.

 

Otherwise, an 80mm achromat is an inexpensive way to test the waters to see whether you really like imaging. Cheaper than the longer tube so you won't think twice about upgrading it if/when the time comes.



#10 Stelios

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Posted 08 July 2020 - 07:41 PM

Apparently you haven't bought anything yet. Good.

 

I suggest you save for this combo. Probably the least expensive ready-to-go combo. 

 

If this is totally out of the question, consider just saving for the HEQ5/Sirius mount, and just use your DSLR until you can save for a real telescope.

 

The EQ5 is a very limiting mount. The HEQ5 is a totally different class. 

 

Consider also buying used.

 

You want your first scope to be an APO or at worst an ED scope, no more than 600mm F/L. 

 

The problem of starting cheap because you can, is that you will very likely be disappointed by the results, you will have already spent the money, and you are more likely to drop out of the hobby. Which makes the savings into a wasted expense.

 

Whereas if you start with a solid foundation, you will get good images from the start, albeit they will be widefield at first. Then when you can afford the scope, you'll get better, and when you can afford a flattener, even better, and when you can afford guiding, then you'll be set. 

 

Of course that's my opinion. Some people like tilting at windmills, and some windmills *have* gone down in defeat :)


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#11 imtl

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Posted 08 July 2020 - 07:54 PM

I think you should first understand what do you want to do with a telescope. There is no all around telescope. Are you interested in DSOs? Planetary? If DSOs then is it wide field? Faint fuzzies? There is a lot out there.

 

I would not start with a thought about what's a beginner scope or not. I would start by trying to figure out what do I want to see in the night skies.

 

I'm not saying the suggestions given here are wrong. They aren't. They are good for majority of beginners (and for non beginners). I'm just making another point here that's all.

 

Eyal


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#12 Ryou

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Posted 08 July 2020 - 08:07 PM

I think you should first understand what do you want to do with a telescope. There is no all around telescope. Are you interested in DSOs? Planetary? If DSOs then is it wide field? Faint fuzzies? There is a lot out there.

 

I would not start with a thought about what's a beginner scope or not. I would start by trying to figure out what do I want to see in the night skies.

 

I'm not saying the suggestions given here are wrong. They aren't. They are good for majority of beginners (and for non beginners). I'm just making another point here that's all.

 

Eyal

This is also a fairly good point and realistically speaking 600mm is right in that middle range of focal lengths where it's not super deep (galaxies, tight details) and not super wide (whole large nebula, sky + foreground) either.

 

There are definitely different scopes for different things out there, like come the winter I'm planning a massive mosiac and if I was to try taking it with my SVX80 it'd take over 3 months to complete probably due to the size of the mosiac vs field of view. I think I'm still estimating about a month with my SpaceCat though... like I said, massive mosiac



#13 imtl

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Posted 08 July 2020 - 08:22 PM

This is also a fairly good point and realistically speaking 600mm is right in that middle range of focal lengths where it's not super deep (galaxies, tight details) and not super wide (whole large nebula, sky + foreground) either.

 

There are definitely different scopes for different things out there, like come the winter I'm planning a massive mosiac and if I was to try taking it with my SVX80 it'd take over 3 months to complete probably due to the size of the mosiac vs field of view. I think I'm still estimating about a month with my SpaceCat though... like I said, massive mosiac

Right in the middle sometimes mean that you do not have an optimal system for anything. Its better to have a widefield (<500mm) along with a deep sky scope (>1000mm). Of course there is an issue with costs. That is obvious.

 

Just to stick to the theme of this post, I think that getting an 80-100mm scope with a field flattener has great benefits with almost immediate results for a beginner. Going for >600mm will have much bigger chances of getting bad results and frustrations. If expectations are realistic on what a 80mm scope can do then the OP will be happy with his future setup.

 

Eyal


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#14 bjulihn

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Posted 08 July 2020 - 08:31 PM

Hi Eddy;

 

Stelios made a VERY GOOD POINT when he said the the EQ5 Pro is not the same as the HEQ5!!! The HEQ5 is a reasonable AP mount and about the minimum anyone here would recommend to you. I am assuming you know this but I will say it anyway. A quality mount is the FIRST thing to pay attention to! A modest telescope on a good mount will give you very good results. A top of the line scope on a cheap mount with produce junk!  I have no experience with the EQ5 Pro, but do not underestimate the need for a good quality mount. I am using the iEQ30 Pro by Ioptron. It is on the lower mid-range end of their mounts. But I get very good results with both an 80mm triplet refractor and a $350 6" f4 Newtonian. Pay attention to the mount first. If you can't afford something a little better, wait til you can. 

 

We are wishing well in this adventure!

 

Brad 


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#15 eddykhan993

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Posted 09 July 2020 - 06:53 AM

I started with the NEQ5 and an 80/400 achromat. Similar to the ST 120 but shorter.

The longer FL of the ST will make things harder, but it's at a mid point, so maybe not too hard. I'd say you'll still be able to learn a lot with it. The EQ5 should be able to manage 1-minute unguided subs at that FL without too many bad subs.

I'd say go for it.

You will need a flattener, but I wouldn't worry about that just yet. You'll probably want a better tube when you get serious about it. For now, the ST120 will be fun to play with, and the field curvature isn't an impedement at all.

Expect a ton of CA though.

What camera are you planning to use with this?


right now its more use what you got. i have a nikon d5000 and its in great condition. not the best for AP but ive hard ot will do

#16 eddykhan993

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Posted 09 July 2020 - 07:43 AM

Oh, that's right. Sorry. I missed this crucial fact:

I guess the emphasized part implies he hasn't bought it yet. So, what Ryou said, if imaging is your goal, that's not an ideal scope. An 80mm F5 tube is a far better starter option. Easier to handle so easier to learn, and a great FL for many nice bright targets. If your budget allows for an APO or an ED doublet, go for that instead of an achromat. These scopes will provide much better image quality, and they tend to be better mechanically as well, and you'll never really outgrow them.

Otherwise, an 80mm achromat is an inexpensive way to test the waters to see whether you really like imaging. Cheaper than the longer tube so you won't think twice about upgrading it if/when the time comes.


ive just seen a SKYWATCHER STARTRAVEL 80MM EQ1 REFRACTOR TELESCOPE but its says eq1. will that go on a eq5 or heq5? the answer is probay simple but i tend to second guess things. it is 80mm and f5. but its 9nly for £140? cant be right?

#17 OldManSky

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Posted 09 July 2020 - 07:47 AM

The Skywatcher Star Travel 120 has a focal length of 600mm.

It's also pretty inexpensive (around $300), which is probably what drew you to it.

 

You can do some astrophotography with it, but it will likely in many ways be disappointing.

It will have a large amount of chromatic aberration -- "blue bloat" -- that will make your stars look like they've all got huge blue halos.  It's not an attractive look.

It doesn't have a flat field for imaging, so you will certainly want a flattener to take images with it...if you don't use one, it will have round, sharp stars in only the center 40-50% of the image, and as you move outward from there they'll get progressively uglier (looking like blue-haloed comets instead of stars).  A decent flattener/reducer will add another $200 to the cost.  And you'll still have blue bloat.  And the single-speed focuser with limited travel means focusing will be more difficult and might cause you some spacing headaches.

 

As an alternative, I'd suggest something like the AT72 from out host Astronomics ($469) ( https://www.astronom...fpl-53-f-6.html ).

Pair it with the flattener/reducer designed for it ($129), and for less than $600 you have a really nice FPL-53 ED scope that's designed for astrophotography, has very little chromatic aberration, a nice flat field, a dual-speed, terrific focuser, and a 344mm focal length that's great for the bright nebulae of summer and fall.  That's only about $100 more than you'd spend for the Skywatcher 120 and flattener, and you'll have a vastly better setup for imaging.


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#18 klaussius

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Posted 09 July 2020 - 10:31 AM

ive just seen a SKYWATCHER STARTRAVEL 80MM EQ1 REFRACTOR TELESCOPE but its says eq1. will that go on a eq5 or heq5? the answer is probay simple but i tend to second guess things. it is 80mm and f5. but its 9nly for £140? cant be right?

It will probably fit. Dovetails are rather standard, but I'm not 100% sure. Even if it doesn't, getting a replacement dovetail shouldn't be at all difficult or expensive. Buy just the OTA though, without the mount. Or, there's a package that comes with a cheap photo tripod and a backpack. That one's useful if you want to go backpacking with it. I've done it with mine and it's fun. But if it says EQ1 it's that it comes with an EQ1 mount, you won't have any use for that EQ1 if you get an EQ5 or HEQ5 so it's pointless.

 

The option OldManSky gave you is a good one really, if your budget can stretch for it, you should go with that. As I was saying, I started with a small scope much like the ST80, but ended switching to something similar to that AT72 (the SW Evostar 72ED) because I really wanted better optics for widefield. If you can go straight to the AT72 you'll save you some money in the long run and get much better images for it. It all depends on what your budget is for this purchase.



#19 Ryou

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Posted 09 July 2020 - 10:50 AM

Semi-random and slightly off topic so a simple yes or no is fine, however could chromatic aberration/blue bloat show up as grey halos if you were using an O3 filter on mono and did a HOO combine? Granted I'd expect the G and B to be combined in that case so not grey halos... 


Anyways that aside and more on topic... Could anyone actually link me an EQ5? I've seen it mentioned several times as different than the HEQ5 however every time I try searching it I only ever come up with HEQ5s 

 

As for the StarTraveler 80mm scope, it looks like the EQ1 version includes a manual mount, probably the EQ1 mount. The scope (OTA, optical tube assembly) itself does look like it has a bracket that would fit on the HEQ5 if you found the scope by itself. Even if you could buy the scope by itself though this seems like an achromatic scope which as has been mentioned just is not going to do too well. It will work however you'll definitely need to temper some expectations. 



#20 Hesiod

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Posted 09 July 2020 - 11:02 AM

WHile there are "workaround" for chromatic aberrations, there are not for sloppy mechanics.

This is the most excellent reason to stay as far as possible from very cheap "entry level" telescopes if want to take deep sky pictures.

As an example, replacing focuser and mounting rings could be more expensive than purchasing a small 80mm "APO".

 

Anyway, here the eq5

http://skywatcher.co...ct/eq5-synscan/

 

and there the Heq5

http://skywatcher.co...t/heq5-synscan/

 

The eq1 is not a good mount to begin with, and really bad for deep sky AP: in my opinion, among Skywatcher lineup, the first "decent" mount is the eq3 (which, in fact, is the first ready to use a polarscope...).

Do not let you be fooled by the low price as for AP this money is basically wasted.

 

If have already a camera and some lenses may purchase just the mount: lenses up to 200mm are very easy to use, and there are many interesting targets to shot


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#21 RJF-Astro

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Posted 09 July 2020 - 03:29 PM

I often see widefield recommendations for beginners, but I do not think that is a good idea if you have a light polluted imaging site. LP will often introduce complex gradients, which are difficult to process and lead to dissapointing results, much like bloating. This can also demotivate a beginner.

That is why I would say 300-600mm is safer to begin with. The suggested 72 is a good pick, as is an 80.

If you have nice dark skies, things change and going wider in RGB is less demanding on processing skills.

#22 Peregrinatum

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Posted 09 July 2020 - 04:52 PM

best focal length is the one that fits the targets you are most interested in...


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#23 Ryou

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Posted 09 July 2020 - 04:56 PM

While I will not say they are fun to deal with, light pollution gradients can be pretty easily calibrated out in most cases. In fact it may even be more tricky the higher the FL as if you have a framing that is all nebula (which is more common on the higher FL) you run more of a risk of removing that nebula data and need better selections or processing. This exact thing got me on one my first images I ever took where I had an image basically all nebula, tried my gradient reduction I was using before, and just nuked the nebula out of existence. 


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#24 TelescopeGreg

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Posted 09 July 2020 - 11:09 PM

What Peregrinatum said.

 

Within reason, if you're not imaging things that are interesting, you could get bored or annoyed, and that would be bad.  We all would like to take Hubble images from our back yard, sure, so emphasis on the "within reason" part.  But this is a hobby, not a university.  There's nobody driving you to achieve anything in particular, and no tests at the end of the year, other than the goals you set for yourself, judged by the gray matter between your ears.  Take it slow, but do what interests you, learn from making mistakes, and know that bad images can teach you more than good ones as long as you actually look at them and try to understand what happened and how to make them better.  After all, if everything "just worked", what would you have learned?

 

This goes for both the image acquisition (taking subs and calibration frames), and the back-end processing.  Both can be challenging, in different ways, and in ways that appeal to different personal interests.  I like tinkering, and hate spending hours pushing pixels around with a mouse.  So my scope's configuration is a bit more challenging to operate than most "beginner" setups, but I rely on DSS and StarTools for processing.  You decide what's right for you.



#25 RJF-Astro

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Posted 10 July 2020 - 02:30 AM

While I will not say they are fun to deal with, light pollution gradients can be pretty easily calibrated out in most cases. In fact it may even be more tricky the higher the FL as if you have a framing that is all nebula (which is more common on the higher FL) you run more of a risk of removing that nebula data and need better selections or processing. This exact thing got me on one my first images I ever took where I had an image basically all nebula, tried my gradient reduction I was using before, and just nuked the nebula out of existence. 

Calibrating light pollution? As far as I know calibration takes care of vignetting and amp glow, but not LP. You do this in post processing.

 

Anyway, this is the kind of gradients I am talking about. This is a fully calibrated stack of the markarian's chain with a 135mm on an APS-sized sensor.

 

20200328 markarians.jpg




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