First scope - Bresser Messier Dob 8" Question/s

[stevenbmkiv]

Good morning all,

I picked up my first scope (Besser Messier 8") from the very helpful guys at Tring Astro on Friday.

I built up the base without issue.

The tube mounting was simple enough too.

I also purchased a 1.25" variable polarizing filter, Two Baader Hyperion 68deg 8mm and 17mm eye pieces after discussing which ones to buy.

The OTA came with the 25mm Super Plossel eyepiece.

I looked at the Skywatcher Dobs but I was sold on the fact the Bresser is mountable on either mount types in the future should I wish to and the nice rack & pinion focuser with both 1.25" and 2" options.

Clear skies last night meant Sat night was my first opportunity to use it.

However, all I got was a blurred image of a star with the circle and cross wires in the centre. I zoomed in/out using the focuser with each of the three eye pieces too but the same scenario happened.

I am new to telescopes but I am not sure this was right. I was advised the scope should have been collimated from the factory and shouldn't need adjusting at all.

I even tried removing the 1.25" eye piece adaptor and using both Hyperion lenses into the 2" ring instead. Same scenario.

All protective caps were removed.

I also find the movement of the scope quite difficult and am already starting to think the Skywatcher model would have been better.

The base turns fine and I can loosen off the lock nut ok if needed but up and down movement is stiff as the mounts don't seem to be very forgiving with movement up and down and one side will keep popping out of the base unit leaving the scope tilted sideways until I pop it back in place.

Working Mon-Fri next week means I can't pop in to get the scope checked and next weekend the guys are off to the Brecon Beacons so it will be two weeks time before I can get it looked at.

I have an allen wrench and I am pretty capable with setting things up once I know what I am doing so if anyone can recommend a few things to check, that would be great.

I have attached pictures of the eye pieces I am using as well as the new addition itself.

Any help appreciated.

Kind regards

Steve

[ronin]

I even tried removing the 1.25" eye piece adaptor and using both Hyperion lenses into the 2" ring instead. Same scenario.

All protective caps were removed.

Usually you remove the 2" adaptor then put the 1.25" adaptor back in all on it's own.

The 1.25" adaptor sits in the 2" one for shipping purposes, then people leave both in (because it all looks right) and get totally confused. That is the situation on Skywatcher ones and I suspect the same on yours.

Also you imply that the secondary was close to being visible and that is a symptom of the above - the eyepiece is held too far back.

Take the 2" adaptor out and drop the 1.25" adaptor in, that should "move" the eyepiece inwards.

Cannot help on the movement, I would suspect that something is a bit tight or that they are intended to e as it is.

I would say some people prefer a scope to swing easily and some what to make a definite push to move them, perhaps these are set to the stiffer option, at least initially. I guess there will be some adjustment.

If the OTA is jumping out then that sounds like one of the side units is loose or at least flexible, so it will move and pop out comes the OTA. For this I suggest you gently check for movement and if there is what appears to be too much then head back to Tring with scope to ask them. The images do not show the front of the scope as I would half suspect there shuld be a brace across the uprights to maintain them in position.

[Stu]

It looks like a nice design, good to see someone thinking about these things and coming up with a new style product.

Regarding the stiffness of movement, what is on the bearing surfaces between the scope beating and support? They should not be in full contact, but should have a couple of pieces of PTFE at either end of the support which the bearings run on. Are these there?

Some scopes also have little tabs at the side to keep the bearings located correctly but it doesn't look like this one does.

Can you lift the scope off and post some images of the bearings and the support?

Sure you will get it sorted.

[SnakeyJ]

I also like the design of this, especially the big open rocker and R&P focuser. You've also picked up some decent EP's.

Perhaps have a go in daylight if you can find something 1-2km and well clear of the sun. Easier to see what you are doing and will give you a chance to align the finder.

[stevenbmkiv]

Thank you for the replies.

I read up about the 2" adaptor possibly being the culprit. However, upon removing the 2" adaptor the aperture of the hole is far to big for the 1.25" piece to sit in.

The 2" eye piece part is bolted directly to the focuser and from there the 1.25" slides into the 2" and from there the eye piece is inserted. Jane @ Tring Astro even showed me this.

There is a small allen bolt grub screw which I have loosened but the 2" adaptor will not budge and I don't want to be rough with it just incase it's not meant to move.

I think the base unit is fairly tight at the moment and probably a little bit of silicon lub spray will help. The mounts rest on the base by way of two plastic pieces each side and have a textured metal plate on them to allow movement and the mounts also have the same plastic material used for tabs to help keep it secure from the inside of the mount.

The rotation works in the same way in the plastic round feet sit on the base turntable and rest/slide on a textured metal surface.

Pictures attached to show both the mount detail and the focuser and eye piece.

I wanted a Dobsonian as I want to learn the sky. I did almost buy the Celestron Nexstar 6SE/8SE but thought the Dob would be more fun to use and has the future mounting options to think about.

Steve

[stevenbmkiv]

Sorry, I meant to say that I removed the 1.25" eye piece adaptor. I can't see how the 2" adaptor can be removed thus allowing the 1.25" adaptor to fit.

Unless I'm missing something very obvious.

[Stu]

That all looks right Steven. Normally the surface on the bearings is smooth, something like Formica, are you saying these ones are textured? That seems a little unusual as it would seem to make movement more difficult. Some form of silicon spray may help though as you say.

Regarding the eyepieces, it seems to me you are doing the right thing with the adaptor. The only thing I can think is that the hyperions are both 1.25" and 2", have you tried using them directly into the 2" part of the focuser without the 1.25"?

Last question, and apologies if you've answered this already, is it I focus or out focus you are running out of? ie, are you needing to fully rack the focuser in and still not reaching focus, or vice versa?

[Ju Piter]

sounds like back focus problems i have to use a 2" extention for my 2" eps and a 2" to 1.25" adapter with extention for my 1.25" eps did you not get any with the scope ?

[Ju Piter]

why does it not have 2 ptfe pads each side look like 1 per side surely that will make it stiffer ?

[John]

It looks an interestingly designed scope but these are very new to the market (you are the 1st owner that I've heard of) and there may be some teething problems that will need to be worked around.

The focus issue is nothing to do with collimation - it's simply that you have not yet been able to get the eyepiece to the right distance from the tube wall to match the focal point of the scope optics, which is usually somewhere between 2,3 or even 4 inches outside the tube wall. Eyepieces do not all have the same focal plane themselves but there is usually not much more than 1cm either inwards or outwards difference.

Your focuser setup and the adaptors look OK to me - the Hyperions and the plossl should come to sharp focus - ie: no shadow of the secondary and it's supports across an unfocussed disk of light. The focusser might need to be racked most of the way in to achieve this though. You need to experiment more perhaps ?

As set up in the photos, the tube looks too far down the rings and it looks as if it will not be able to point above a certain angle ?. Maybe thats just how it was when the photo was taken though.

On the altitude movement, the design is very much like the one I use on my 12" dobsonian and that uses 2 teflon pads on each side running against a laminate wrapped around the alt bearing (the half wheel like structure on your dob). The principle works really well but something might be snagging / dragging somewhere giving you the unwanted "sticktion". If the teflon pads are pinned in place (mine are glued) check that the pins / staples are recessed below the level of the teflon surface so that they don't drag against the laminate.

I'm sure you will get these niggles sorted and enjoy the scope. It looks a neat design

[stevenbmkiv]

Thanks guys.

Yes, there are two teflon pads each side. I just showed one for close up purposes. There is also a teflon pad on the inside edge where the rockers are to stop them falling off track.

The actually rockers themselves have the textured metal plating along the outer curve which rubs against the teflon pads, same principle for the base with round teflon feet along a ring of textured metal.

I have some silicon spray I can use to help things slide better.

I had used both Hyperion EP's in the 2" adaptor and got the same effect. So I covered all avenues with all eye pieces with focus right in and out for both 1.25" and 2".

Do I need further eye piece extenders then?

Steve

[John]

....Do I need further eye piece extenders then?

Steve

With a little expermentation you should be able to work out if you need more outward or inwards travel to reach focus. For the former you can loosen the eyepiece a little in the drawtube and try pulling it gently out to see if if reaches focus. If you need more outwards focuser travel you can get an extension tube to sort that.

Do these experiments at night on astro objects by the way. Terrestrial things are far to close generally to be any help.

If you are running out of inwards travel, that is the unfocussed disk of light from a bright star / planet seems to be getting gradually smaller and closer to focus but won't quite get there before the focuser runs out of inwards travel, then it's a more complex issue to sort out. Either the primary mirror would need to be moved up the scope tube a little or a lower profile focuser is required. If the scope does not allow for enough inwards focuser movement to bring relatively normal eyepieces such as yours to focus then someone has specified the wrong focuser for it

[laudropb]

Try focussing on a distant object in day light. You can try to align your finder at the same time. It is much easier to see where possible problems are in the light of day. Use the 25mm eye piece in the 1.25 adapter. The supplied eyepiece should be able to reach focuses.

[John]

Try focussing on a distant object in day light. You can try to align your finder at the same time. It is much easier to see where possible problems are in the light of day. Use the 25mm eye piece in the 1.25 adapter. The supplied eyepiece should be able to reach focuses.

I'm not sure about that - terrestial objects are so much closer that they will require the focuser to be racked out much more and may mask, rather than reveal, the issue. I've seen reports of folks who can reach focus on a terrestrial object, even quite a distant one, but still can't when viewing a celestial target.

[ronin]

I think you are going to need to contact Tring and ask about the 1.25" and 2" inserts.

Specifically:

"Is there a 2" adaptor in the focuser for 2" eyepieces and when using a 1.25" eyepiece and the corresponding adaptor does the 2" insert need to be removed. And if it does how is it removed ?"

Seeing the shadow of the spider is normal when the focuser cannot get sufficent inward travel and at least on the Skywatcher items this tends to be using both eyepiece adaptors in the focuser at the same time.

[Stu]

I think answering the question which John and I asked will help isolate the problem ie do you need more in focus or out focus. If you rack the focuser right out, then loosen the eyepiece and pull it further out, does the 'donut' get smaller or bigger? If it gets smaller it implies you need more out focus so an extension tube would be needed.

If you rack the focus in, and the donut is getting smaller but you reach the end of the focus travel before reaching focus then you have a bigger problem and something needs sorting by Tring I suggest. They should sell you a system which works together correctly, so best to check with them before doing anything else.

[stevenbmkiv]

Thanks guys. I will play around with the eye pieces tonight and move them in and out to see if that helps. I can speak to Tring tomorrow at work.

Got some DIY to do during today so no chance to check in the daylight either.

ps. I'm learning as I go along so this will all help me.

[Stu]

Thanks guys. I will play around with the eye pieces tonight and move them in and out to see if that helps. I can speak to Tring tomorrow at work.

Got some DIY to do during today so no chance to check in the daylight either.

ps. I'm learning as I go along so this will all help me.

Good stuff. I'm sure you'll get it sorted soon, looks like a nice scope.

Keep us posted as to how you get on

[stevenbmkiv]

Just tested it again usiing the 25mm Super Plossl and I extended the focuser out to the max and then pulled out the eye piece and just as I got to the end where it came out of the adaptor I got to see the stars!

So it seems like an extender tube is needed.

To be fair to Trin Astro, it was their first Bresser in and they had only recently built it up. So perhaps they were unaware of what was required.

Can anyone recommend a high quality extender tube to accompany my set up/eyepieces?

Thanks again

Steve

[John]

Just tested it again usiing the 25mm Super Plossl and I extended the focuser out to the max and then pulled out the eye piece and just as I got to the end where it came out of the adaptor I got to see the stars!

So it seems like an extender tube is needed.

To be fair to Trin Astro, it was their first Bresser in and they had only recently built it up. So perhaps they were unaware of what was required.

Can anyone recommend a high quality extender tube to accompany my set up/eyepieces?

Thanks again

Steve

Your supplier should provide you with a suitable extension tube free of charge I'd have thought - at the moment they have supplied you with a scope that won't reach focus

You get extension tubes in different lengths. Did you note how far above the max extension of the focuser you needed to put the eyepiece to reach focus ?.

You need an extension tube that will be a bit longer than that so you don't need to have the focuser racked out to the max to achieve focus.

I assume you will use a 2" extension tube and then you can put your 1.25" eyepiece adapter in the end of that.

Common sizes for extension tubes are 35mm and 50mm. You can get longer but not, as far as I'm aware, shorter ?.

[stevenbmkiv]

Thanks John.

I'll call Tring Astro tomorrow and see what they say. I suppose you are right in that a scope should be usable of course, just like anything else.

I extended the focuser out to the max (40) and then pulled the eyepiece right out so that literally the end was just touching the adaptor.

Sounds like I need a 50mm piece at least then.

There was another piece in the box.........I just remembered now. I wonder if that was it.

Will check it out tomorrow but it didn't look like one from what I remember.

[John]

The 2" extenders that I've used look like this:

http://www.altairastro.com/altair-50mm-extension-tube-2x-thumbscrews.html

[stevenbmkiv]

Hi John,

Last night I found the piece I was looking for. It was threaded each end too. The reason I dismissed it previously was because I thought it might have been a camera mount.

Basically, where the 2" adaptor is fixed to the focuser I found the little allen grub screw undoes, then I unscrewed the 2" adaptor, fitted on this other piece then refitted the 2" adaptor followed by the 1.25" adaptor. I didn't get a chance to test it out but it looks about 50mm in depth so I am guessing this is what was needed.

The instructions supplied were non existent and what made me chuckle was that the simple base building instructions stated 'these are not the full detailed instructions, see main pack for these', accept there were no others, not even on the supplied CD Rom disc.

Oh well. If it turns out the piece supplied isn't what I need, I know what to get but I would hazard an educated guess and say that it is right.

Clear skies tonight required......

[Stu]

Good stuff Steve, that certainly sounds like it will do the trick.

I guess the scope has been designed for visual with the extender, and to have enough infocus without it to reach focus with a DSLR

Hope you get clear skies soon, forecast not good here.

[stevenbmkiv]

_{Thanks. Yes, it is typical. Get the scope sorted at last and then clouds for days ahead. Still, Gives me a chance to lube the Teflon pads and loosen the turn table a tad more.}

_{Can't wait.}

_{My wife saw the new addition for the first time last night as I bought it while she was away. She is excited to use it too.}

_{I appreciate all your helps guys. I couldn't have managed without your knowledge.}

_{In the meantime I have the books coming through the post from Amazon. Turn Left at Orion and the Philips Planisphere book. Learning how to use a Planisphere too.}

_{Cloudy night reading!}