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Hey guys it's me agaiinn. Recently I have been thinking about which telescope i should buy(its going to be my first telescope!!!!!) I have narrowed it down to 2 choices! The Skywatcher explorer 200p and the Skywatcher explorer 200pds

I just can't seem to chose oneee.

I want to do Astrophotography and i have heard that the Dual Speed focuser is going to help a lott. can someone please explain how? I m a total newbie and have just begun reading about Astrophotography. 

On the other hand i ve heard that some eyepiece s will need an extension tube to help them achieve focus (due to the secondary mirror placed closer to the primary) and i really want to see through the telescope my self.I dont know if the extra 140€ that i have to pay to get the focuser and the pds and eq5 (rather than just getting the 200p and eq5 combined ) is worth it .Does it really make that big of a difference?? I hipe somebody can help me

 

Thanks

 

-Kronos

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The PDS is made for astro imaging - yes you probably will need some extra spacing for visual use.

The P will not need any spacers but if ever you use it for imaging you probably wont have enough 'in' travel to achieve focus which is harder to correct than adding a spacer to a PDS

Personally I would choose the PDS if there is any chance of using it for imaging. The focuser is much nicer too.

As a note of caution - the 200 is a big scope for an EQ5 mount - not really a good match for imaging.

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With fast scopes, critical focus zone is very tight. You need very good precision to focus stars to pin points when doing astrophotography.

With observing it is not that critical because eye can accommodate small focal shifts, but many people prefer dual speed focuser for visual also - it makes finding perfect focus much easier.

With astrophotography process is much more involved - you focus where you think is right place - take image, check if it is focused, adjust focus, take another image, repeat until you have perfect focus. With dual speed focuser it is much easier to do small adjustments and this reduces number of iterations to get precise focus.

I'll echo concern from above - EQ5 and 200PDS is not going to be best imaging platform. EQ5 is suited for much smaller scopes.

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Damnittt .it was just on my budget (with all the accessories involved) i cant find better mounts anywhere close to my pricerange ! Can you suggest some good mounts for the 200pds? (Inside of the uk because greece (where i live) has a law that says every package that comes outside of the European Union will charge us a ton of fees) (probably more than the mount itself) my buget is around 400€ for a solid mount , thanks

 

 

Kronos

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What are your priorities? Visual or astro photography?

I'm asking this because people often want all in one package to be able to do both, but requirements for those are quite different, as is price. Astro photography tends to be expensive compared to visual.

Sometimes it is worth having two separate systems - one for visual and one for AP. It is also important to have an idea of what level of performance do you want from your AP system.

For visual side of things in 8" range you simply cannot do better than 8" dob. This scope however is very unsuitable for astro photography. On the other hand, having 400€ budget for mount for AP is adequate for very basic stuff. In that sort of budget you can get EQ3 class mount, and only thing that you can sensibly mount on such scope is DSLR + Lens, or maybe very small imaging refractor - up to 3kg total.

If you can stretch your budget for the mount to EQ5 class mount, that would be much better, but then you need to pair that with suitable scope - again small refractor or small reflector - something like 130PDS. You can maybe get EQ5 class mount for that sort of budget if you go second hand, or skip goto version and go for basic version and motorize it yourself. Something like this:

https://www.firstlightoptics.com/skywatcher-mounts/skywatcher-eq5-deluxe.html

+

https://www.firstlightoptics.com/sky-watcher-mount-accessories/enhanced-dual-axis-dc-motor-drives-for-eq-5.html

but it will probably be less accurate than regular Eq5 goto version

If you are serious about AP, I would recommend HEQ5 as your first mount. This mount would be able to hold 200PDS, but it is more than twice your current budget for the mount. You would also want to guide it and you would need additional bits like coma corrector (which you should get for any sort of imaging with newtonian scope) - and you can see how fast expenses mount up.

Back to the original question of 200p/pds on EQ5 mount - I'm guessing that you want that for both visual and to try AP. In that case, you might want to think about following:

- I would not recommend EQ mount for visual with newtonian scope and I think that dobsonian mounted 8" will be much more useful visual instrument, but that aside, if you get for example 200p on Eq5 mount and use it for visual and maybe planetary ap with suitable camera (even DSLR) and try long exposure astro photography for practice, and then after some time you get your self second scope for imaging - something like 130PDS, once you had a go at AP and learned basics of imaging and processing. Just bare in mind that results will not be that good with 200p on Eq5 and there will be some frustration - which does not need to be frustration if you are aware that it is not very suitable combination - you just take some images and don't stress your self if results are poor - it is process of learning until you get smaller / lighter imaging scope that will give you better results.

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FIrst of all thank you for your time! Second of all i have decided to buy a 8” dob that costs 320Euros(skyliner 200p)  for visual. I ve thought of something i dont know if its true or not: I think i would get better results with an eq5 and a cheaper refractor due to being able to do more exposure time so i ll gather more light overtime rather than having a large aperture and tracking for less.If i am right there should be refractors that are well suited for astrophotography in the 300€ range  that go well with the eq5 .Again if i am right can you suggest some?

 

thanks

 

kronos

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8 minutes ago, Kronos831 said:

FIrst of all thank you for your time! Second of all i have decided to buy a 8” dob that costs 320Euros(skyliner 200p)  for visual. I ve thought of something i dont know if its true or not: I think i would get better results with an eq5 and a cheaper refractor due to being able to do more exposure time so i ll gather more light overtime rather than having a large aperture and tracking for less.If i am right there should be refractors that are well suited for astrophotography in the 300€ range  that go well with the eq5 .Again if i am right can you suggest some?

 

thanks

 

kronos

200p dob is excellent scope - I have one and I'm very very pleased with it for visual. I think you will be happy with yours.

On topic of refractor vs reflector for imaging and aperture size, things are not as simple. I can try to briefly explain some aspects to help you decide but topic is complex one and you might want to research further (or ask additional questions).

For imaging you want to get at least ED refractor or APO triplet. Regular doublet refractors (without ED elements) suffer from chromatic aberration - making stars bloated in images and having purple halo around bright stars. It is very hard to find imaging refractor in 300euro price range because of this.

Reflectors are much more affordable in this regard.

Astro imaging is done by stacking of multiple exposures (in part due to restrictions in tracking precision). Fewer longer exposures is always better than many shorter exposures each adding to same total amount (for example 10 exposures of 10 minutes will be better than 20 exposures of 5 minutes, although they both add to 100 minutes total). However difference between the two (few long vs many short) depends on read noise of your camera and sky conditions. If you use low read noise camera or shoot in light pollution (almost all sky now days has some amount of light pollution it is very hard to find dark sky - you need to go many hundreds of kilometers away from larger cities/towns) difference will be very small.

On the other hand - larger aperture gathers more light in same amount of time - so larger scope has advantage there (same as for visual). Problem with larger scopes is two fold - harder to mount - you need stronger mount because of added weight, and also focal length is getting longer and this means that your field of view is getting smaller, but it also means that light is spread over larger surface (think of it as zoomed in) - so you receive less light in each pixel.

As you see, it is not so straight forward to decide which is better - small refractor or small reflector, and each needs to be considered in what is offering and how good it will work for particular targets and then you can decide which one is better.

Let's take 300euro budget and see what are options in this price range (we will probably need to go a bit over budget).

Refractor - this is about only imaging refractor that you can get for that sort of budget:

https://www.firstlightoptics.com/pro-series/sky-watcher-evostar-72ed-ds-pro-ota.html

depending on camera used (and I believe you plan to use some sort of DSLR), you will need this also:

https://www.firstlightoptics.com/pro-series/skywatcher-85x-reducerflattener-for-evostar-72ed-pro.html

but that is almost 200e so total price is now close to 500e - much over budget

On this web site you can check what sort of field of view you will get with this scope (with/without flattener) and your camera:

https://astronomy.tools/calculators/field_of_view/?fov[]=2654||61||0.85|1|0&messier=42

Reflector - again, really one contender for ap (you can also consider 150pds but it is more expensive and heavier - some people used it on eq5 but I would recommend 130pds instead):

https://www.firstlightoptics.com/reflectors/skywatcher-explorer-130p-ds-ota.html

and you will need coma corrector for it, so something like this:

https://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html

That together will be much closer to your budget at 320e total

In each case you need to add T2 adapter for your DSLR (around 20e) so you can attach your camera to telescope.

Just for comparison, here is field of view with Canon 450 and above to scopes:

image.png.a124c529a9cb9c6c7fe95cab637b0594.png

As you see, it is not really straight forward choice, refractor will be more expensive, but will probably suit you better for starting with imaging - larger FOV so you will be able to capture brighter and larger targets with ease. For galaxies, clusters and planetary nebulae - reflector is better choice although it has smaller field of view (these targets are smaller so it is well suited). Refractor won't need collimation and is a bit easier to work with, reflector will need collimation ...

This is just beginning by the way ... if you get serious with imaging, at some point you will want to auto guide and that is a bit more expense :D (not much, you can actually guide with 50mm finder scope, guide cam and suitable adapter, so another around 200e investment, but you can do that later on if you decide).

 

 

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Once agaiin thanks so much! You have madd things a little more clear!I was thunking of buying the 72ED too I don’t understand why i need that reducer .The 72 ed is just about what i can spend. do you think i can combine it with an eq5 and do decent dso imaging? If not can you please suggest the best telescopes for dso imaging that can be used on an eq5 for decent\good d s o imaging ??

 

thanks

 

Kronos

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Main purpose of reducer / field flattener in case of 72ED is not reduction - it is field flattening.

Focal plane of telescope is not flat surface, it is part of sphere, and thus curved, like this:

image.png.97997aaa5f864966988b02012f01a65e.png

Camera sensor on the other hand is flat surface. This means that if you focus on a star in center of the field of view, stars at the edges will be slightly out of focus, and if you focus on stars near the edge, center will be a bit out of focus. If there is field curvature present, it is best to focus on a star that is about 2/3 from center towards the edge of the field.

Field flattener is designed to compensate this and bring all points in focal plane to single focus. With visual this is not a problem as eye can accommodate to very slight focal shifts. Larger curvature can be problem even for visual.

You can certainly use 72ED without flattener, result will be smaller FOV (because flattener by its design also shortens focal length a bit so it's acting as reducer as well, although it is not is primary purpose) and you will have to be careful how you focus. With fast ED doublets and fast APO refractors even careful focusing will not help - some of stars will simply be larger and slightly out of focus - usually at edge of field of view.

This is what it will look like in image (extreme example - in your case it certainly won't blur as much, this is just to get idea what this aberration really is all about?

image.png.7d2299ae4ea007f8065d993c6d750346.png

Like I said, I would recommend above two scopes as suitable starer scopes for EQ5:

Skywatcher 72ED - you can use it without field flattener (and add one maybe later), but be prepared for some field curvature - slightly soft stars in outer field, or depending where you focus at (like 2/3 from center) - a bit soft stars over whole field by uniformly defocused.

Skywatcher 130PDS with suitable coma corrector. Coma is another type of aberration that is inherent in parabolic mirror scopes. It affects outer parts of the image, but unlike field curvature, it can't be reduced by careful focusing. You need another type of optical corrector - called coma corrector to eliminate it. Here is what coma looks like in the image:

image.png.33873c3ab23722a0275052e746c6502f.png

For more information on Skywatcher 72ED and what curved field looks like, take a look at this discussion:

https://www.cloudynights.com/topic/636980-sw-evostar-72ed-in-the-house/

(there are some test images - see post #24, mind you those are taken full frame sensor and depending on your DSLR, your field might be smaller and aberration less pronounced, if you have APS-C size sensor for example)

For Skywatcher 130PDS and its performance as imaging scope, have a look at dedicated thread here on SGL:

A lot of images there were taken with EQ5 / 130PDS combination, so you can see if you like them and if it's the right thing for you.

 

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The P/PDS. there have been a number of very good images taken using the 200P on an EQ5 mount it's just a tad bit more demanding of your time.

see link below to one SGL member who used this very system for a number of years.

http://astrocasto.blogspot.com

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