8" Bresser for EAA (& more...?)

[Boron]

Hi, 

I've been wanting a telescope for what must be the last twenty years but never had the time/budget for one. I got lucky recently with a market find that I picked up today, a 2005 Bresser Messier 203/900 (F4.4) Newtonian. 

Its in pretty good, but not perfect, shape, and I need some help both in identifying what needs to be fixed and holes in my plans for what I plan on doing with it - I'd appreciate any comments here since I am reasonably well read but havent really entered the hobby before.

Photos

Needs fixing:

1 - Sticker on the OTA is great and identifies it exactly, but I need some help with the mount. I think its like the OTA, and is a 2005 era EXOS2 but it is in need of a bit of love. A few hand knobs and the polar guide scope port cover are missing and the previous owner mentioned that there should be an accessory tray that fits between the legs and gives the tripod more rigidity that he tried to get back with the attached steel cable - but from what I can see the top of the legs make solid contact with the body so this doesnt appear to be the case. Bresser have some replacement parts available but the tray they have only sits there between the tripod legs and acts like a spacer rather than a truly structural element. 

1b - If it is an EXOS2 then my plan is to slap a Onstep kit onto it and use largely as-is.

2 - I dont know if the focuser is any good by "modern" (not 20 years ago) standards. It appears to be fairly standard rack and pinion single speed. 

3 - Guide scope is 50x8 and surprisingly solid with a nice etched (?) glass reticle in it. The eyepiece rubber has perished and there is some grit on the inside but it appears it diassembles readily. Am I ok to use IPA here to clean it up?

3b - Not sure if I'm going to swap out the bracket for a more standard dovetail and keep the scope in a new set of mounting rings. 

The Plan:

So where I am in Norway we have a lot of cloud cover that should lessen a bit now that the temperature is dropping as we move towards autumn and winter. Winter can be bitterly cold (-30 not unusual here), but it does mean the skies are clear. With this in mind I wanted a scope that will suck as much light as possible in as short a time as possible to maximise any windows where observing is possible - and this 8" fast newt is better than I had any reasonable expectation. I also wanted this to be GOTO'd with an Onstep kit and run both a power extension and looooong USB cable to the scope in my back yard and treat it as a somewhat remote observatory, staying nice and warm inside.

I planned to hunt DSOs - nebula and galaxies. 

For an imaging setup I had provisionally identified a Player One Neptune as being desirable. I found a thread on Cloudy Nights about Etendue that has an equation for comparative signal strength ratios between setups and using this in a spreadsheet the Neptunes came out pretty well. That said its a pretty simplified equation and I suspect the relative pixel size terms are doing some very heavy lifting and leaving out a whole bunch of detail about the physics. Not sure about the tradeoff in shooting with a colour/mono camera since that would then need a bunch of filters and maybe automatic filter wheel with additional cost and complexity.

I know as newtonian a coma corrector is high on the priority list, as is a collimating eyepiece.

Is there anything else I have missed here or made an obvious mistake with?

[Jim Franklin]

Initially I would try to clear debris from any glass surface with air - gently blowing from a pipet blower initially, if there is stubbon deposits, for any optical cleaning I would only do with warm deionised water - I know others may have doifferent opinions on this, but I have always only ever used either RO or commercailly bought deionised water to clean optical systems where they need it - but I try to avoid it.  Do not use cloths on the glass surfaces - they will leave scratches. - let water run off but dry with a warm (never hot) hair dryer. 

Collimation is critical - the optics will never perform at their best unless kept collimated - I would suggest a Celestron Laser collimator - I have one - brilliant and easy to use - works on my Newtonian and my SCTs. 

The accessory tray on nearly all the scopes I have owned or seen is only ever really that - yes, they will often lock up against the legs in a semi structural way, but this is more stability that strength - if you can get the tray I would suggest you do. 

Rother Valley Optics stock Besser Kit, and they actually have the same mounts new - they may be worth contacting for spares https://www.rothervalleyoptics.co.uk/bresser-messier-exos-2eq-5-mount-tripod.html

First Light Optics stock Bresser equipment, but I was unable to find any mounts on their website - they are worth speaking to as well. https://www.firstlightoptics.com/

Looking at the picture of the mount on the Rother Valley site, the central tray looks the same as the Skywatcher accessory trays - that may be an avenue worth exploring. 

[CraigT82]

All sounds good. Should make a nice EEA set up. The mount is a bit small with that scope on board to do long exposures, not impossible by any means but difficult. 
 

You will want to look at motorising the focuser too if you want to operate remotely. A mini PC for scope and mount control mounted on the scope itself will do all the controlling and you can then operate that mini pc from indoors over USB or WiFi, using a laptop or tablet, or even phone with an app. Check the distance though as both may struggle if it’s quite a long way and you’ll also need to consider signal boosters. 
 

You may also want to attach a smaller planetary/guide camera to the finder scope to allow you to guide but also use the polar alignment routines in software like sharpcap.

[CraigT82]

Oh and you can add pics straight into the thread, no need to link to a hosting site on here.

 

[PeterC65]

I use an Explorer 200 with a Uranus-C camera on an AZ-EQ5 mount for EAA and that combination works well for smaller objects. The Neptune-C has the same pixel size as the Uranus-C but a smaller sensor and so a smaller field of view.

One of the big differences between doing visual astronomy and EAA is that for EAA your field of view is much more restricted. With an eyepiece I can go from 9' (at 3mm) to 2° (at 30mm) with the Explorer 200, but with the Uranus-C I'm stuck with 38.5' (even less if I use a Barlow). With your Bresser and a Neptune-C you will get 30', with a Uranus-C you would get 43'. At 30' you will be getting to the limit for plate solving which is one of the big benefits of EAA. The Uranus-C (or any IMX585 based camera) is a great camera by the way.

The way to get a wider field of view unfortunately is to invest in a shorter focal length scope! I now have five, plus a camera lens!!

I don't use a coma corrector for EAA. I've studied the star shapes from both my Explorer 150 and 200 and they just don't need one. I do use a field flattener with my refractor though.

If EAA is what you plan to do (rather than AP) then I'd recommend a colour camera. Monochrome cameras will be more sensitive for faint objects but another of the great advantages of EAA is that you get to see the colour within objects and that is pretty spectacular for most objects.

I would try to get a tray for your mount. Mine screws up towards the mount head, locking the legs apart, and it adds considerably to the tripods rigidity.

You will probably want a focuser with fine adjustment (a second 10:1 reduced knob). Even for visual I find this useful, and it is almost essential for the accurate focus needed with a camera.

 

[Boron]

So its been about two weeks since posting this and the shine of my then new purchase has dulled somewhat, to the extent that this evening I've been wondering if I wouldnt actually be (financially, at least) better off with buying a cheap Svbony Mak or 100mm Bresser maksutov since it might turn out cheaper doing that than it is to correct some issues with the scope.  Norways import tax puts a significant damper on things.

@PeterC65 I'm encouraged by your reply here addressing the coma issue - but do you have any images from them to set my paranoia at ease? I had settled on the Neptune CII but after some light persuasion on another forum another user pointed out that the Neptune 664 has a response curve that is finely attuned to IR so have decided to pick that up instead. EAA is definitely the goal, temperatures drop precipitously in my part of Norway in the winter (also providing most of the clear skies we will get) and standing outside doing visuals in -10 to -30 degree nights in meter deep snow just doesnt appeal. 

At some point down the line I will need to pay some attention to "winterizing" the scope to allow it to function in such temperatures and I'm not entirely sure if adding a fan to draw freezing air into the tube is going to be beneficial or whether adding heater elements is going to be correct. Dew is obviously not so big of a consideration when prime observation time coincides with sustained significantly below freezing temperatures.

Fine focus adjustment is at least something I believe I have sewn up on the solution front, there is an EAF winging its way to me and I am deciding on a new focuser with a 10:1 element.  Determining the focus point - by which I mean the focal point distance away from the OTA tube and thus the required focuser extension height - has proved difficult and I'm wary of needing such an array of adapters and extensions that it looks like my newt has taken up smoking.

Edited September 11 by Boron

[PeterC65]

9 hours ago, Boron said:

@PeterC65 I'm encouraged by your reply here addressing the coma issue - but do you have any images from them to set my paranoia at ease?

Here is M1 and surrounding stars taken with the Explorer 200PDS without any coma corrector but with a UV / IR cut filter ...

This is what I was seeing on the night using SharpCap, with no post processing.

Because I'm inside in the warm, I find that my EAA sessions can be long, and then dew becomes a problem. I've been struggling to combat dew with the Explorer 200 and so far have tried:

• Adding a dew shield which may make some difference but the main benefit seems to be preventing stray light from entering the scope.
• Adding a dew heater strap to the primary which prevents dew build up on that mirror but does nothing for the secondary.

I've considered adding a dew heater to the secondary but they need to be glued to the back of the mirror and then have a cable run along a spider vane through a hole drilled in the side of the scope, and I don't fancy doing that. So I've fitted the secondary with a cover which is meant to reduce dew, and fitted a fan (home made) to the primary to blow some of the warmed air from that end of the OTA up to the secondary. This has yet to be tested in anger.

Most electronic focusers fit to the coarse adjust side of the focuser, and once fitted, they prevent manual control. So with an EAF (I assume you have bought the ZWO) you don't need a fine adjustment focuser. The EAF will give you fine control and it can be controlled using a hand controller if you do happen to do visual astronomy. Astroasis are the only people I'm aware of who make an electronic focuser with a clutch which can be disengaged for normal manual control (I'm getting one of these at the weekend).

The focus point, and what adaptors you need, varies with the type of scope. With my Explorer 200PDS I need a 35mm extension and 13mm of focuser extension.