teoria_del_big_bang

46 minutes ago, Grierson said:

Could I ask a naive question. Assuming the filters are inside a filter wheel, as in this case, and the width has wheel has already been included why is it necessary to include the thickness of the filters in the calculation? Thanks - John   

Because the glass in the filter refracts the light path and alters the focal point. So add 1/3 of the thickness of the glass of the filter.

Thanks to @andrew s for the drawing.

I took the drawing from this thread but the thread is a little confusing as it talks about adding 1/3 of the filter thickness and also subtracting it but as it pushes the focal point further back then you definitely must add it.

do-filters-add-to-back-focus

Steve

@Juicy6 Out of interest what is the thing ringed in red below?

Steve

Looking at the photo I had in my first reply the numbers didn't add up so had to think what I actually did and why I had the 20 mm spacer and not a 19.5 mm spacer.

That was actually an old photo.

The distances on the top row (6.5 + 29.7 + 20 + 8 ) actually add up to 64.2 which is 0..5 mm longer than the required 63.7 mm. This is because the nearest spacer I had was 20 mm and had to use this to begin with. Eventually I bought  15 mm + 4 mm + 0.5 mm spacers to make it correct. To be honest I am not sure I could see any difference when it was 0.5 mm incorrect.

But i think it did answer your question  

Steve

I had same issue as I had a HEQ5 when I got the scope and swapped the saddle clamp for this one:

geoptik-universal-dual-load-mounting-saddle-plate

However you do need the puck to go with it:

geoptik-adaptor-puck-for-heq5-mounts-to-use-universal-mounting-plate

So is about another £50. Personally I would go with this better option, the smaller one may do okay I cannot really comment. Ring the supplier or send email and ask them they will tell you for sure.

Steve

5 minutes ago, Stuart1971 said:

There is normally a threaded hole in the end of Losmandy dovetails, usually in the centre,  for a stop bolt to be fitted, all mine have these, and then a bolt should be screwed in to the front end, to stop it sliding out backwards... 👍

Yes that's all that is needed but not sure it's in the one supplied (but easily added).  Also the supplied losmandy is pretty short so not sure it is long enough to do that, depends on where centre of gravity is and where it ends up in the clamp when balanced I suppose.

The clamp is more expensive and over-kill but also means I can place it exactly at the balance point so making balancing much easier. Also I had the clamp and needed to do with it 🙂 

Steve

Just be real careful. When I got mine I was searching other threads about this scope and read one horror story about one person's rig slipping on the mount and he only just caught it before it crashed to the floor. I will see if I can find it again.

I think he claimed that the losmandy as supplied is slightly narrower than normal and as it was a pretty short clamp it did not tighten quite right in the clamp. Not sure how true this is about the width but for the size of scope (and weight) it is pretty short. So I bought a longer losmandy and fitted a clamp so that it cannot slip back any further than the clamp when I put it on the mount even of not clamped fully tight. Maybe a bit over-kill but this was too much money to risk dropping it on the floor and I am clumsy 🙂 

Steve

It will be worth it - you will like the scope (a lot).

1 minute ago, Craig123 said:

Thanks Steve. Really appreciate that from an Esprit owner . I saw the 63mm in the manual  but a few threads on the net had 56mm mentioned and the extra attachment for FF  had me stumped abit. 

No problem, happy to help. 

One reason I now always take a picture of the final setup is that often determining this back focus is not straight forward and obvious and sometimes the spacer size is not easily obtained as a standard size. In my case a 20 mm spacer was pretty close and the 1mm just brought it in almost exactly. Although never done any tests to see how much an issue an odd 1 mm or so error would make.

Steve

Just double checked and I think we are both right. The distance is 63 mm but that includes the 8mm thick spacer that you are measuring from so in that case it would be 55 mm.

But astill do not forget to correct for the thickness of the filters as this could add up to 1 mm if they were 3 mm thick.

Below is from the manual:

Steve

I need to double check but I thought the back focus distance should be 63mm from the edge below where it says 100 Field Corrector to the image sensor.

Also do not forget to add 1/3 of the thickness of your filters. In my case they were 2 mm so needed to add 0.67 mm (or approximately 0.7 mm ).

I also have the Esprit 100ED, a filter wheel which according to documentation is 29.6 mm wide (but measured it at 29.7 mm) and the AS1600 and have the following:

Seems to work fine for me. 

EDIT: The above is actually an old photo. The distances on the top row (6.5 + 29.7 + 20 + 8 ) actually add up to 64.2 which is 0..5 mm longer than the required 63.7 mm. This is because the nearest spacer I had was 20 mm and had to use this to begin with. Eventually I bought  15 mm + 4 mm + 0.5 mm spacers to make it correct. To be honest I am not sure I could see any difference when it was 0.5 mm incorrect.

Steve

Very nice, clear and sharp image 🙂 

Steve

+1 for the LP filter unless you are in a dark skies anyway, you can get one that clips direct into the DSLR camera .

Light Pollution Filters

Steve

Hi,

Firstly welcome to the forum 🙂 

In theory you can place the Asair anywhere you wish ond on the face of it if it is secure then where it is it would work fine.

However, the main advantage of any mini computer is to reduce any cables that move when the mount moves and hence eliminate cable drag that can cause issues if not managed well as the scope tracks the target. With the mini computer mounted on top of the scope itself all cables to the asair could be in a fixed position and you do not need to leave a loop to account for the movement, only with the 12V power cable .

Steve

There are issues getting a normal SW 130M to focus with a camera attached. Usually people by the 130 P-DS that has a much shorter tube length when used for astrophotography. 

What is involved to be able to do this with the 130M I am personally not sure but hopefully someone here can help you.

Steve

Hi and welcome to the best Astro Forum there is.

I could not add to what vlaiv has already said - very good advice indeed 🙂 

Steve

On 30/07/2020 at 11:27, saturnian said:

Hi,does anybody know if the Kelling Heath Star Party – Autumn 2020 is officially cancelled?

Thanks

I would like to go to this if still on. According to website there is no indication it is cancelled and can still book lodges, pitches etc.

Steve

I guess you could always either redrill the new saddle to suit or make (or get one made)  an adapter plate.

Steve

Do you mean the vixen dovetail saddle as in replacing with somethings better ?

Steve

Welcome to SGL, a great place for friendly advice or just a chat 🙂 

Steve

Yes great idea I can see that one catching on with many members on here. Hope you have a very swift recovery and get to use your scope and treat soon.

Steve

With that setup (not exactly planet killing) I think that is brilliant image 🙂 

Steve

I have a couple of these clamps and they are a lovely piece of engineering but on a cold night when I have numb fingers at best of times I was never sure they were tight and also struggled to loosen them. Hopefully this will solve the issue 🙂 

Steve

14 minutes ago, StevieA said:

I am looking foward to it. When I was young the sky always seemed so clear, even in town! But having spent many years near Cambridge I am used to sodium yellow!!!

In comparison, my new sky's are gorgeous!! Perhaps the lure of a quieter, less hectic lifestyle might help the missus appreciate a location with darker skies!! lol 😆

Steve

Sounds great I love Norfolk and Suffolk. I have tried the lifestyle thing but she is quite a lot younger and still working so that didn't work.

Steve

Welcome to SGL.

Must be something about the mid fifties that's when I got my first scope ever and never looked back.

That was just over a couple of years ago so as a relative newbie I am maybe not the best member to give advice. However, as my aspirations were very similar to yours with wanting to progress to some astro photography I can tell you my path on this amazing hobby obsession.

I too had a similar budget maybe pushing the £1K at most. Best advice I would have is to spend wisely as you often just want to get into it and when you look on these websites there seems a load of scope / mount bargains out there but all may not suit your needs.

The AP side of also leads to other questions as planetary and DSO's really require different scope and camera setup. What is constant between these though is that for imaging you really need a really sturdy mount capable of tracking the object and so you need to be spending probably a larger part of the budget on the mount than the scope. Even 2nd hand you will be spending around £500 on the mount (ideally - not saying people do not manage images from mounts for less but it does add to the difficulty).

After getting some great advice from members on SGL I initially snapped up a 2nd hand Dobsonian for about £120. Then bought a couple of extra eye pieces and that did me for several months whilst I gave a lot of thought to what I wanted to do on the AP side of it and my future equipment buys and saved up a bit more capital. The Dobsonian was great and gave some great views of the stars, a few galaxies and because it was not a goto but very manual also in my opinion really helped me get used to where some of the objects were in the sky.

My plan was to get rid of the Dobsonian when I went onto imaging but still have it for observing, maybe I will part with it someday but doubt it. Whilst in this initial stage I kept saving and by looking at other peoples images and threads on here decided I preferred the DSO side of things and then bought a 2nd hand HEQ5 mount which is a real good start for imaging mounts, bought a smallish refractor, guidescope and a 2nd hand DSLR and started on the imaging. 

Be warned though it is really addictive and soon have several scopes and now a dedicated astro camera and bigger mount so well exceeded my £1000 budget (but that really is up to you but honestly very easily done).

Anyway enough from me for now, but money wise if you buy good equipment, even 2nd hand, look after it, then you will be able to sell it on if you want better which really helps you progress and save on the cash. Even from new if looked after can often recuperate 2/3's of the initial cost and if originally bought 2nd hand you lose very little.

Good luck with the journey 🙂 

Steve

No problem but if you want me to send you one each of these I am getting to try for size you are more than welcome 🙂 

Steve