James1967

15 hours ago, vlaiv said:

Just a word of caution about OAGs and fast scopes.

Size of OAG prism is important and distance of it to focal plane. With fast scopes - you want your OAG to be very close to sensor - otherwise prism will act as aperture stop. In principle you want your OAG to be closer than F/ratio * size of pick off prism.

Say you have 8mm pick off prism and you image at F/4. You want your OAG prism to be closer than 32mm to focal plane (or rather - imaging sensor).

If you put OAG too far away on small fast scope - you'll make it work as if stopped down.  8mm prism at 64mm away from focal plane and Esprit 80 will work like F/8 guide scope - with just 50mm aperture and 400mm FL. You'll limit light to guide sensor by factor of 2.56!

Got it - understood!  Many thanks, the advice is really appreciated.

Thanks Viktiste.  Certainly sounds good enough for me to give the OAG a try - I’d much prefer this route if I can work with it.

On 11/11/2019 at 09:15, Viktiste said:

I just bought the Esprit 80 ED, and I'm very happy with it so far. The only thing I miss is a proper way to attach a finder scope. The guide scope attachment arrangement works, but is a bit flimsy. I really don't understand why the manufacturer don't make some screw holes in the body dedicated to attaching a finder scope.

Having said that I'm sure you will be happy with the Explore Scientific too, both are good scopes.  

Hi Viktiste.  Rather off topic, but I’m looking at an Esprit 80 ED too and considering OAG (vs guidescope).  Can I ask how you find the ZWO OAG with the ASI 120 MC (as I have one of those already)?  Recommended?

Anyone else with a view would be welcome too!

Thanks for all the responses.  I’m expecting to eventually progress to astrophotography and will therefore likely also get a refractor with much smaller focal length, so I’ll bear that in mind too.  I’ve understood much more now (basically you can’t increase max FOV with the reducer so no point using a reducer AND 2” diagonal/EP.  Need to decide on one or the other).

Probably best for all that I get the scope with provided accessories and play with it before deciding on anything else.  It’s not as if the stars and planets are going anywhere.  Thanks again 😄

25 minutes ago, Laurin Dave said:

I believe that your fov will be limited by the telescope field stop to 46/2350 x57.3deg ie to 1.12deg and that no eyepiece/reducer combo will exceed this ..   It can be quite an expensive lesson to learn as I found out !

Dave

Thanks Dave.  Would you recommend not buying the Evo 9.25” then?  I can cancel it and get something else.  Or did you mean that you spent a lot on EP’s, reducers etc trying and failing to get a wider FOV?

Most DSO’s seem to be much much smaller than 1.12 deg and it’s only a few eg M31, M42 that are much bigger - or am I missing something?

1 hour ago, ollypenrice said:

Yes, still here. I did once try both a 35mm Panoptic and a 31 Nagler in a 10 inch Meade with the 6.3 reducer. I don't remember whether they actually increased the FOV, though I think they didn't. What I do remember was that the view was not very nice and I didn't use that combination.  Sorry but I can't remember what I found stressful about the view. I certainly didn't like it, though. I only used those EPs at native FL.

Olly

Thanks Olly.  Your set up sounds very similar/relevant.  It also makes sense to me (as a novice) that the light path is limited to the 46 (48?) mm baffle width BEFORE it passes through the reducer, so the FOV would not be increased by adding the reducer.  I guess I’ll just have to try the supplied EPs with/without the reducer first and see if the FOV is changed or just the magnification, before splashing out on 2” diagonals, EP’s etc.

Maybe it’s just me but I find it bizarre that field of view impact on various set ups is not a standard piece of information provided, like magnification, focal length.  Guess I’m asking too much. Ho hum.

1 hour ago, John said:

I think the F/6.3 reducers are designed for use with 1.25 inch format eyepieces. With 2 inch eyepieces and large field stops they vignette the field of view I believe.

 

 

Thanks.  I guess the issue is whether the 0.63x reducer, by reducing the focal length, increases the max true field of view (baffle width/field stop x 57.3/ focal length) or not.  Because the light path passes through the limited baffle width before passing through the reducer, I’m not sure the formula is valid for such a set up - but I really don’t know enough either way!  
If the formula is valid in this case, then a 2” 36mm 72 degree AFOV EP *should* work to give 1.75 degree TFOV and it may be worth me experimenting.  I know I can always return the EP’s etc to FLO if it doesn’t work, but it would be easier all round if I could establish how it works in advance. The Celestron website is particularly unhelpful in this regard.  Thanks again

On 26/09/2018 at 12:22, ollypenrice said:

Unless the design of the scope has been altered I think you can acheive the same FOV without the reducer as with it if you have a 2 inch visual back. The field is limited by the baffle tube in both cases so it can be reached with a widefield 2 inch EP at F10.

Olly

If you’re still here, could you use the 0.63 reducer AND 2” EP (eg Baader Hyperion 36mm 72 degree AFOV)?  Per my calculations, this would give a 1.75 degree TFOV for my Evo 9.25” (2350mm focal length, 46mm baffle width), where the theoretical max TFOV for the scope would be 1.78 degrees with the reducer.

(I’m awaiting delivery of the scope so all my workings are theoretical, just using optics maths not practical knowledge)

14 minutes ago, Greymouser said:

Yes, the mount is really excellent, but in my opinion, not quite large enough to hold the 9.25. ( Yes, I have one. ) I think the mount itself is the same one as with the 8" one. I would very much advise limits on where the mount can go, to avoid any unfortunate collisions with the mount!  I cannot remember where I have the limits, but it is easy to do, so no problem, just be careful until you get to grips with it. I would also advise using the hand controller, it is much easier because of the tactile direction buttons. Also I have found it annoying when the app crashes, ruining night vision as my tablet returns to the home screen. Many have no problems with the mount and the 9.25, having it very far forward on the vixen, but that makes me very nervous, so I am extra careful, even though it is still very near the end. ( I may experiment with a longer dovetail if such is available, at some point... ) I agree, there is no pount to the starsense as the mount works so well.

It is though an excellent scope, even better with the reducer, even for just visual. It gives two scope in one basically.  I have the 2" visual back, but do not use it much, prefering the reducer. I would say to get a small refractor to go with it for the wide FOV, as the 9.25 is just not going to do it imo.

Can I ask what maximum true FOV you can see using the reducer (and with what eyepiece, focal length, apparent FOV)?

5 minutes ago, Greymouser said:

Yes, the mount is really excellent, but in my opinion, not quite large enough to hold the 9.25. ( Yes, I have one. ) I think the mount itself is the same one as with the 8" one. I would very much advise limits on where the mount can go, to avoid any unfortunate collisions with the mount!  I cannot remember where I have the limits, but it is easy to do, so no problem, just be careful until you get to grips with it. I would also advise using the hand controller, it is much easier because of the tactile direction buttons. Also I have found it annoying when the app crashes, ruining night vision as my tablet returns to the home screen. Many have no problems with the mount and the 9.25, having it very far forward on the vixen, but that makes me very nervous, so I am extra careful, even though it is still very near the end. ( I may experiment with a longer dovetail if such is available, at some point... ) I agree, there is no pount to the starsense as the mount works so well.

It is though an excellent scope, even better with the reducer, even for just visual. It gives two scope in one basically.  I have the 2" visual back, but do not use it much, prefering the reducer. I would say to get a small refractor to go with it for the wide FOV, as the 9.25 is just not going to do it imo.

Thanks so much, that’s all really useful.  Certainly need to be careful with how high I point the scope etc especially if I have all sorts extra on the eyepiece end.  I didn’t realise the reducer would fit on the standard 1.25” visual back.  I had assumed I would need the 2”.  The small refractor is another good option I’ll bear in mind.  I’ll just have to double check when I’ve played with it ‘as is’ for a while and worked out what I want to do.  Many thanks again. 👍

2 hours ago, Highburymark said:

You’ve ordered a very nice piece of kit. The 9.25 is a large scope but comes with a beefier tripod. A new diagonal is the first and most important upgrade in my opinion. The stock one is poor. New visual back is also a good idea. As the Evolution already has an excellent go-to system, I don’t think Starsense is necessary. Save your money and get a couple of nice eyepieces - though at F/10 it’s a forgiving scope so most eyepieces will work well.

Many thanks Mark, that’s good to hear - eyepieces are deffo on the list once I’ve tried out the standard ones. Can’t wait 😄

Ok, after lots of research, I finally decided on the above and just ordered with FLO.  Now got a few weeks wait so can keep exploring the sky manually with by binoculars and learn as many pitfalls as possible about the Evo 9.25”.  The only accessory I ordered for now is a dew shield, but I’m expecting I will want to get a 2” visual back, star diagonal and wide angle eyepiece (possibly 0.63 focal reducer too) to get the max field of view possible when I so choose.  Any views on whether StarSense is worth it - it seems pretty simple to align without it (I may come to regret saying this)

So why am I posting?  Just after any and all advice for a beginner, in particular regarding maximising field of view down the line (the relatively narrow FOV was the only real downside of the Evo 9.25” for me) and any recommended accessories to enhance my viewing pleasure over time.  Any other general top tips also very welcome. 

I look forward to being able to help others in due course when I have something more than roughly zero knowledge and experience!

On 03/01/2017 at 20:22, Filroden said:

I can get between 30s and 60s depending on where in the sky my object is. Objects in the East or West directions and with altitudes lower than 60deg are best to minimise field rotation. I have gone out as far as 90s but with my camera I see no additional benefit. I'm better stacking 3 times as many 30s exposures (it's only a 12bit camera but with very low read noise).

This is an image I'd taken with the 80mm refractor and a Canon EOS 60d.

Here's one taken with the refractor and a ZWO ASI1600MM-C:

Wow! They are stunning. 

6 hours ago, IanC11 said:

And one other big tip. get yourself 3 pieces of wood, 6"x 6" x 3/4"+ , put these under the base feet and it stops the feet sinking into soft ground.

 

That’s fantastic Ian, thank you so much for all the recommendations and tips, really appreciated.

Thanks Ian.  That makes sense too, comparing with the 27kg for the 10” stated on the German website I found.  
Can I also ask which accessories I should buy upfront.  Most people say ‘wait and see’ which is my approach, but things like dew shields or heaters seem pretty much required (I’m in North Yorkshire).  Any tips warmly welcome.  
thanks again,

James

6 hours ago, John said:

 

Hello and welcome to the forum.

Here is a more recent thread on the 300P Synscan dobsonian which may help on the general portability / practicality of these scopes:

Thank you so much Neutron Star, that’s really helpful.

what a great community here 😃

5 hours ago, jacobingonzo said:

Hey James

 

I recantly purchased the 300 flextube- I have transported it in then car a few times- Im mid 50's generally good health but just a stubby 5'7 and not muscly either but managed it ok- little bulky but manageable in shortish carrying sessions- I managed to put  the base in the boot of my seat leon saloon with no real issues- Its the Tube thats a heavy bleeder- but just be sure footed and take your time- tube and base are manageable if you take it easy

I fashioned a DIY trolly to sit the base feet in- 4 lockable wheels did the job-really handy when moving it about generally and observing.

 

J

Brilliant, that’s just what I wanted to hear.  The tube seems definitely to be just over 20kg (but without carrying handles that make it feel tougher to carry I guess).  It was the base/mount that concerned me, so you’ve answered my question.  DIY trolley sounds just the job too 👍 Many thanks.

6 hours ago, IanC11 said:

Skywatchers site says shipping weight is 21kg + 23kg with the tube weighing 21kg so that would make the base around 20Kg ( the smaller of the 2 packages when shipped )

Thanks.  The only SW website I could find was showing the one without the goto, motor drive etc, here

http://www.skywatcher.com/product/bk-dob-12-collapsible/

this has the same weights that you mentioned.  This one below says 46kg total for goto.  Around this weight is fine (each weighing about a full suitcase - no issue for me)

https://www.apm-telescopes.de/en/telescopes/dobsonians/skywatcher-dobsonian-skyliner-250p-flextube-synscan-goto-dobsonian

to be honest, these are fine, but I saw somewhere on SGL (can’t find now, sorry) a mention of ~40kg+ just for the base/mount, which would be prohibitive.  I’ve fired off a few emails to suppliers too now, so I’m sure I’ll get to the bottom of it.  Thanks again.

You don’t happen to have one to sell do you - save me waiting for the new stock? 😄

On 23/09/2013 at 10:54, nicks90 said:

i would second what Avocette says above,

the 300 flextube is fairly heavy if you are of slight build or have a bad back, joints, [insert malady here].

I collapse my OTA down, but leave a 4" gap between the top and bottom parts. To move it, I grab the primary mirror casting with my right hand and my left hand goes in the 4" gap next to one of the truss sections and i hoik it around like that. That way I have a firm grip with my fingers on two parts of the scope, which in my opinion is slightly safer than one hand gripping and the other 'cuddling' the ota. Also has the advantage of being able to twist your body and tube about to get past obstacles and though narrow gates etc.

The base is big, heavy and awkward - although mine is the tracking version with motors - but either way the truss tube 300 dob bases are taller than non truss tubes and therefore heavier and more awkward.

If i had to move mine about more than the 20 feet from my garage to the back garden / boot of my car, I would seriously reconsider the 12" and look at a 10" non auto / non flextube designed dob.

Nick

Hi Nick, I’m new on here and looking at getting a SW flextube 300 goto.  My concern is the base weight as I’d prefer to put in the car and take 20 mins to a darker sky site though I would use in my back garden too.  Do you know or can estimate the weight of the base (without the OTA on)?  I might have to go for a 250 or even 200 if the 300 weight is too much.  I’m a fairly fit but not muscly 6’2” 53 yr old bloke if that helps.