8" Bresser Dobsonian - Finderscope Replacement

[Xilman]

When I saw the title, I thought you were going to use an 8" OTA to replace your finder ...

[PeterStudz]

On 17/08/2024 at 21:21, nige745 said:

That looks really good! I had forgotten about dew shields 🙄 What are they made out of & did you buy them or make them?

That's a great idea with the phone mount, where did you get it from and how have you mounted it to the OTA? 

I also like the adjustable stool.

Thanks! The dew shields are homemade and made out of a black yoga mat with thin veneer bonded together with Evosik contact cement. However, it was not planned quite this way. On its own I found that the yoga mat that I brought was too thin and floppy. So I stuck on some very thin veneer that I had down my shed. The veneer was originally for model aircraft wings. It’s easy to make your own just out of a yoga mat or camping mat. Just make sure it’s thick enough! If you search this site and the internet you should see plenty of DIY examples. And Evostik sticks the mat together really well. Out of interest - the veneer is lighter than the plastic mat - so you get a lighter overall dew shield. 

I find dew shields invaluable. Not just for keeping dew at bay (getting dew on the finder is annoying too), but for keeping out any stray light. For planetary I find this vital as you are going for very subtle differences in colour contrast. 

The phone mount is a combination of a bicycle/motorcycle handlebar phone mount plus a tripod phone adapter. I have a handle on my Dob which  I’ve used as the “handlebar” to attached the adapter. It was from eBay, although offhand I’m not exactly sure where. However, you can use a smartphone tripod adapter or bicycle/motorcycle adapter. I have found that the all metal motorcycle type to be the best. And try and avid those that rely on a spring to secure the phone - they are fiddly and risk the OTA being moved when you install/remove the phone.

If you don’t want to drill holes etc you can used a strong double sided tape to attach the adapter to OTA. When I first tested the app I just stuck my iPhone directly to the OTA using the magnets on the back. Surprisingly it worked very well, but I always had the worry that it would be knocked off. But thinking about it there’s the possibility of making a more secure magnetic holder out of bits of wood. The wood, or whatever, preventing the phone sliding and also possibly falling off. 

[JOC]

FWIW I tried dew shield on my 8" Skywatcher Dob and found that yoga mats were far too heavy and completely over-rode the 'sticktion' that kept the telescope pointed at the target without sagging at the nose.  In the finish I purchased a commercial one second hand which was far lighter and fit for purpose.

[PeterStudz]

Replacing the finder, adding a Telrad, smartphone, large 2” eyepiece… can all upset the balance. Although when I looked into dew shields some of the commercial ones are surprisingly heavy too. If it bothers you ask the weight before purchase.

However, the Bresser Dobs have nice, big, “proper” altitude bearings plus tube rings which makes it easy to balance before a session. 

[nige745]

4 hours ago, PeterStudz said:

Thanks! The dew shields are homemade and made out of a black yoga mat with thin veneer bonded together with Evosik contact cement. However, it was not planned quite this way. On its own I found that the yoga mat that I brought was too thin and floppy. So I stuck on some very thin veneer that I had down my shed. The veneer was originally for model aircraft wings. It’s easy to make your own just out of a yoga mat or camping mat. Just make sure it’s thick enough! If you search this site and the internet you should see plenty of DIY examples. And Evostik sticks the mat together really well. Out of interest - the veneer is lighter than the plastic mat - so you get a lighter overall dew shield. 

I find dew shields invaluable. Not just for keeping dew at bay (getting dew on the finder is annoying too), but for keeping out any stray light. For planetary I find this vital as you are going for very subtle differences in colour contrast. 

The phone mount is a combination of a bicycle/motorcycle handlebar phone mount plus a tripod phone adapter. I have a handle on my Dob which  I’ve used as the “handlebar” to attached the adapter. It was from eBay, although offhand I’m not exactly sure where. However, you can use a smartphone tripod adapter or bicycle/motorcycle adapter. I have found that the all metal motorcycle type to be the best. And try and avid those that rely on a spring to secure the phone - they are fiddly and risk the OTA being moved when you install/remove the phone.

If you don’t want to drill holes etc you can used a strong double sided tape to attach the adapter to OTA. When I first tested the app I just stuck my iPhone directly to the OTA using the magnets on the back. Surprisingly it worked very well, but I always had the worry that it would be knocked off. But thinking about it there’s the possibility of making a more secure magnetic holder out of bits of wood. The wood, or whatever, preventing the phone sliding and also possibly falling off. 

I've looked into dew shields since asking you, as with so many other bits/things/zooms/eyepieces...…!🙃 My head hurts, in a good way, sort of.

I've ordered a black 10mm thick yoga mat already. I really like the look of your shields. They look smart & also don't appear to sag, which is something I was worried about. Putting thin veneer on is a great idea.

I realised after asking about the phone mount my dob doesn't have a handle on it like yours. I've bought a cheap gel phone case which I'm going to stick some Velcro to the back of. I've also got some Velcro straps to go around the OTA. I will stick the gel case to those straps, hopefully. I thought about using magnets, but my phone seems to be quite sensitive to magnets which affects the phones compass.

Also found myself a similar adjustable stool. I think I have nearly spent as much on extra bits as the scope cost me. I have tried to be frugal and have nowhere near bought the expensive stuff. I had absolutely no idea how much everything cost & there's quite a bit of stuff I haven't even got yet 😬 

4 hours ago, JOC said:

FWIW I tried dew shield on my 8" Skywatcher Dob and found that yoga mats were far too heavy and completely over-rode the 'sticktion' that kept the telescope pointed at the target without sagging at the nose.  In the finish I purchased a commercial one second hand which was far lighter and fit for purpose.

I am going to make a counterbalance from some tiny dumbbells and neodymium magnets wrapped in a microfibre cloth. Might not be the prettiest of things but it serves a purpose. Got the idea from Reflactor on YouTube: 

Thank goodness for Google & YouTube!

3 hours ago, PeterStudz said:

Replacing the finder, adding a Telrad, smartphone, large 2” eyepiece… can all upset the balance. Although when I looked into dew shields some of the commercial ones are surprisingly heavy too. If it bothers you ask the weight before purchase.

However, the Bresser Dobs have nice, big, “proper” altitude bearings plus tube rings which makes it easy to balance before a session. 

This is why I'm making a counterbalance.

[PeterStudz]

Hi @nige745… the yoga mat that I used is 4mm thick. I had a look on eBay but the exact one I ordered isn’t available anymore, but there must be others. I did a little write-up here…

If you have an iPhone I found that, with experimentation, it “ignores” any magnet that directly below. After all, there’s a damn great magnet built into the back of the phone. However, avoid anything remotely magnetic, even metal, to the sides. 

I’ve used something often referred to as “taxi magnets” as counter weights. They are relatively heavy on their own, but you can (as I’ve done) add lead to the magnet via the handy bolt at the top. Here’s an example. You might be able to find them cheaper is you look around or by more than one or two. 

https://www.ebay.co.uk/itm/115852216461?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=L24DJmLTTRy&sssrc=4429486&ssuid=I8jCpZsmREe&var=&widget_ver=artemis&media=COPY

[900SL]

I just put a dew shield together from cheap cell foam camping mat. Cut it to a slight taper and fitted round the focuser. It's lightweight foam and holds its shape well.  Measure once, cut twice 😆 

 

Edited August 20 by 900SL

[nige745]

3 hours ago, PeterStudz said:

Hi @nige745… the yoga mat that I used is 4mm thick. I had a look on eBay but the exact one I ordered isn’t available anymore, but there must be others. I did a little write-up here…

If you have an iPhone I found that, with experimentation, it “ignores” any magnet that directly below. After all, there’s a damn great magnet built into the back of the phone. However, avoid anything remotely magnetic, even metal, to the sides. 

I’ve used something often referred to as “taxi magnets” as counter weights. They are relatively heavy on their own, but you can (as I’ve done) add lead to the magnet via the handy bolt at the top. Here’s an example. You might be able to find them cheaper is you look around or by more than one or two. 

https://www.ebay.co.uk/itm/115852216461?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=L24DJmLTTRy&sssrc=4429486&ssuid=I8jCpZsmREe&var=&widget_ver=artemis&media=COPY

I have a Samsung S22. It's really suspectable to the magnetic wallet case it's in. When I take the phone out of the case there's a massive difference. I first thought there was an issue with the phone until I looked online.

The taxi magnets are a good idea. I was thinking about hanging some weights from the bottom of the OTA and they would work fine.

3 hours ago, 900SL said:

I just put a dew shield together from cheap cell foam camping mat. Cut it to a slight taper and fitted round the focuser. It's lightweight foam and holds its shape well.  Measure once, cut twice 😆 

 

That looks spot on. I like how you've stuck the edges together, it's very neat. I am going to use @PeterStudz idea of putting veneer around the foam, but I'm going to try some sticky back plastic vinyl or wallpaper instead of the veneer as it's quite a bit cheaper.

In my case, I usually measure 3 or 4 times 😉

Edited August 20 by nige745

[bosun21]

I've made several dew shields in the past and a few failures. Using 1cm thick yoga mats I tried to make one for my 12" and 10" dobsonians but they continually sagged. I obviously needed some sort of veneer like @PeterStudz has done. I ended up having to buy proprietary dew shields for them. My 7" Maksutov on the other hand is just fine with the yoga mat on its own. I like my dew shields a bit longer than the store bought ones. I use dew heaters on my RACI.

Edited August 20 by bosun21
Typo

[nige745]

1 hour ago, bosun21 said:

I've made several dew shields in the past and a few failures. Using 1cm thick yoga mats I tried to make one for my 12" and 10" dobsonians but they continually sagged. I obviously needed some sort of velcro like @PeterStudz has done. I ended up having to buy proprietary dew shields for them. My 7" Maksutov on the other hand is just fine with the yoga mat on its own. I like my dew shields a bit longer than the store bought ones. I use dew heaters on my RACI.

From watching several YouTube videos, the thicker the foam the better. It increases stability and helps with insulation. I'm going for 10mm which looks a similar thickness to @900SL dew shield. One video suggested if the mat is ribbed, to put them on the inside to help disperse any stray light. Not too sure that this will make a difference, but I'm going to try it anyway.

[bosun21]

2 hours ago, nige745 said:

From watching several YouTube videos, the thicker the foam the better. It increases stability and helps with insulation. I'm going for 10mm which looks a similar thickness to @900SL dew shield. One video suggested if the mat is ribbed, to put them on the inside to help disperse any stray light. Not too sure that this will make a difference, but I'm going to try it anyway.

Yes that's the one I used 1cm = 10mm. The mat I used was also ribbed which I obviously placed on the inner surface. It is working just fine on my 180mm Maksutov despite being longer than store bought versions.

 

[PeterStudz]

Yes, I also prefer a dew shield that’s a bit longer than the commercial ones. I don’t think thickness matters that much, as long as it’s stiff enough to hold a good shape. 

My mat was also ribbed and I placed it on the inter side. If nothing else it just makes it easier to clean and wipe down. If there’s a lot of dew everything will literally be dripping!

Edited August 20 by PeterStudz

[900SL]

16 minutes ago, PeterStudz said:

Yes, I also prefer a dew shield that’s a bit longer than the commercial ones. I don’t think thickness matters that much, as long as it’s stiff enough to hold a good shape. 

My mat was also ribbed and I placed it on the inter side. If nothing else it just makes it was an easier to clean and wipe down. If there’s a lot of dew everything will literally be dripping!

I vaguely remember a formula somewhere, dewshield minimum 1.5 x aperture in length, preferably longer. Mine is around 300mm projection

[John]

On 17/08/2024 at 21:31, nige745 said:

Does the light shield do the same as flocking? Surprise, surprise, I've not heard of a light shield 😆

Sorry - I missed your question.

I used some flocking as well as the light shield although I did not flock the whole inside of the tube. I flocked the area of the tube opposite the focuser and the inside of the tube for the 6-8 inches immediately above the primary mirror.

As I said in my earlier post I've not had any dewing issues with dobs so the half-moon light shield was purely to reduce ambient light impact on contrast, which it did, substantially.

Don't feel that you need to do all this stuff before you use the scope though - dob mods are generally incrementally added. Getting practical observing experience is just as important, if not more so 🙂

[bosun21]

1 hour ago, John said:

Don't feel that you need to do all this stuff before you use the scope though - dob mods are generally incrementally added. Getting practical observing experience is just as important, if not more so 🙂

Exactly John. I would use your scope as it arrives and gain the vital observing skills you will be adding to for the rest of your years at the eyepiece. Adding the mods incrementally is what I did. That way you can discover what is clearly beneficial and what isn't.

[Ratlet]

1 hour ago, bosun21 said:

Exactly John. I would use your scope as it arrives and gain the vital observing skills you will be adding to for the rest of your years at the eyepiece. Adding the mods incrementally is what I did. That way you can discover what is clearly beneficial and what isn't.

I agree with this.  It's easy to go in with both feet and never use half the stuff.  Get the dob and see how you get on.

[PeterStudz]

1 hour ago, bosun21 said:

Exactly John. I would use your scope as it arrives and gain the vital observing skills you will be adding to for the rest of your years at the eyepiece. Adding the mods incrementally is what I did. That way you can discover what is clearly beneficial and what isn't.

I also fully agree. When I first got a small reflector I hurriedly and impatiently put it together without really knowing what I was doing. I hadn’t a clue about things like collimation and the RDF was put on back to front. However, it was a clear night and the moon was in a perfect position. I had a great first session and was not disappointed. 

When I got an old second hand 8” Dob for free (it did not even have a base, and was way out of collimation). Again it was a clear night, so I propped it up on our garden sofa and randomly looked at some stars. The views were surprisingly decent. 

[nige745]

On 20/08/2024 at 18:40, John said:

Sorry - I missed your question.

I used some flocking as well as the light shield although I did not flock the whole inside of the tube. I flocked the area of the tube opposite the focuser and the inside of the tube for the 6-8 inches immediately above the primary mirror.

As I said in my earlier post I've not had any dewing issues with dobs so the half-moon light shield was purely to reduce ambient light impact on contrast, which it did, substantially.

Don't feel that you need to do all this stuff before you use the scope though - dob mods are generally incrementally added. Getting practical observing experience is just as important, if not more so 🙂

Watching another YouTube video & he flocked opposite the focuser & around its edge. I have seen others that flock the entire tube. Flocking 6-8 inches above the primary mirror is a good idea, although I would still have to remove the primary mirror (😬). I will have the odd bit of stray light when out in the garden. Only if I go right down the garden will it be totally light free. I need to find a space down there to be able to set my telescope up first.

Great advice about not doing all this before I use the scope! I want to see what it is like on its own before doing the modifications.

On 20/08/2024 at 20:21, bosun21 said:

Exactly John. I would use your scope as it arrives and gain the vital observing skills you will be adding to for the rest of your years at the eyepiece. Adding the mods incrementally is what I did. That way you can discover what is clearly beneficial and what isn't.

Absolutely.

On 20/08/2024 at 21:27, Ratlet said:

I agree with this.  It's easy to go in with both feet and never use half the stuff.  Get the dob and see how you get on.

I concur.

On 20/08/2024 at 22:00, PeterStudz said:

I also fully agree. When I first got a small reflector I hurriedly and impatiently put it together without really knowing what I was doing. I hadn’t a clue about things like collimation and the RDF was put on back to front. However, it was a clear night and the moon was in a perfect position. I had a great first session and was not disappointed. 

When I got an old second hand 8” Dob for free (it did not even have a base, and was way out of collimation). Again it was a clear night, so I propped it up on our garden sofa and randomly looked at some stars. The views were surprisingly decent. 

Ha haa, I'm worried about setting stuff up correctly.

 

The first thing I will change is the finderscope. I've bought this already along with a Telrad & may mount that at the same time. I'm going to take all of this advice on board. The finderscope is not such a big mod and will make viewing through it easier as its right angled. All of the other bits & pieces I've got or want, I will add as time goes on. Seeing what the telescope does before them will give me a good baseline on how it performs & how the mods perform. Honestly, I can't thank you guys enough for all of the help & advice. I'm so glad I came here to SGL. I have no doubt I will be a regular question asker from now on!!!

[John]

Another couple of tips if I may 🙂

- For your first sessions with the scope pick easy to find and easy to see targets. Although 8 inches of aperture can seen quite faint targets, easy ones to start with such as M81 / M82, M57, M27, the double cluster in Perseus etc, etc will give you some satisfaction while honing your skills for the more challenging stuff.

- I find that ending a session with a familiar and easy to see target is more satisfying and motivating than leaving off after trying something harder and not quite getting it. It's good to leave yourself hungry for the next session I find 🙂

[bosun21]

3 hours ago, John said:

Another couple of tips if I may 🙂

- For your first sessions with the scope pick easy to find and easy to see targets. Although 8 inches of aperture can seen quite faint targets, easy ones to start with such as M81 / M82, M57, M27, the double cluster in Perseus etc, etc will give you some satisfaction while honing your skills for the more challenging stuff.

- I find that ending a session with a familiar and easy to see target is more satisfying and motivating than leaving off after trying something harder and not quite getting it. It's good to leave yourself hungry for the next session I find 🙂

Funny you should say this as I always finish my observing sessions on an old favourite in the eyepiece. I never thought about why I did this up until now. Always better to end your night with a smile on your face as opposed to a frown ☹️.

[Pixies]

Oh sorry. Completely missed this thread. 

Went through the same things a few years ago when I got the Bresser dob. Back then (before the finder adapters were available) the go-to finder shoe was the Baader universal:

https://www.firstlightoptics.com/finders/baader-universal-quick-release-finder-shoe-base.html

 

This was recommended by several people, including the late, great JohnInDerby (whose advice was always the best).

I managed to replace the original shoe with the Baader one without having to drill any holes (although I needed to blank an old one). 

Here it is with enormous 60mm RACI

[nige745]

On 22/08/2024 at 11:08, John said:

Another couple of tips if I may 🙂

- For your first sessions with the scope pick easy to find and easy to see targets. Although 8 inches of aperture can seen quite faint targets, easy ones to start with such as M81 / M82, M57, M27, the double cluster in Perseus etc, etc will give you some satisfaction while honing your skills for the more challenging stuff.

- I find that ending a session with a familiar and easy to see target is more satisfying and motivating than leaving off after trying something harder and not quite getting it. It's good to leave yourself hungry for the next session I find 🙂

All and any tips are more than welcome! This is a great little bit of advice, especially to someone as new to this as me. Also ending a session on something familiar is a good idea. It is something that I am going to stick to. One thing I am particularly looking forward to finding is M104. It never occurred to me that I could actually see this galaxy with my own telescope! I have got so much to learn 🤯

[nige745]

On 22/08/2024 at 14:34, bosun21 said:

Funny you should say this as I always finish my observing sessions on an old favourite in the eyepiece. I never thought about why I did this up until now. Always better to end your night with a smile on your face as opposed to a frown ☹️.

Most definitely.

23 hours ago, Pixies said:

Oh sorry. Completely missed this thread. 

Went through the same things a few years ago when I got the Bresser dob. Back then (before the finder adapters were available) the go-to finder shoe was the Baader universal:

https://www.firstlightoptics.com/finders/baader-universal-quick-release-finder-shoe-base.html

 

This was recommended by several people, including the late, great JohnInDerby (whose advice was always the best).

I managed to replace the original shoe with the Baader one without having to drill any holes (although I needed to blank an old one). 

Here it is with enormous 60mm RACI

I was looking at this same shoe. I've picked a cheaper one up from Amazon but if it's not right then I will go for this one. I watched yet another YouTube video and they put some rubber underneath the shoe to stop it from slipping. It didn't look that nice but it worked.