PeterStudz

Just come in after a session with the 200p Dob on the Sun  (white light) and Venus. Seeing was excellent. Best views of Venus that I’ve had.  Could get up to x375 and it was still sharp with only a slight occasional wobble. First time that I’m anywhere near sure that I could see some subtle variations in the clouds. And it is subtle, like a mottling. My daughter (I never mentioned anything) said that see could see it too. Although her eyes are definitely better than mine! If you have the time tonight I’d take a look. 

3 minutes ago, Franklin said:

The results folk get from AP are totally amazing but there will always be something magical about looking through an eyepiece.

I agree. And although I see the attraction of AP I could not just do AP - I would always, always want to look through an eyepiece. Anything else just doesn’t compare. 

I often use smartphone snaps to record what I’ve seen. Sometimes it’ll only be a picture of the telescope and kit, my daughter using the telescope etc. To these I’ll attach (in the image Caption) a whole observation report. Are we just talking about AP images or telescope/kit snaps as well? 

But when I’ve posted my pictures in the Smartphone/Tablet section of this site I’ve often wondered if I should also include the whole observation report (after all, it’s for images). Generally I don’t, although I have tried a few times. Sometimes I’ve written a report in the observing section and then posted pictures in the smartphone section. I guess one way to do it would be to write a report in the observing section and then link to the pictures in the smartphone section. You could also link smartphone images back to a full report. But then it just starts to get confusing!

5 hours ago, Piero said:

For my 16" dob, I used embossed FRP and teflon for both altitude and azimuth bearings.

Every 6 months or so I lubricate the FRP with a wet bar of soap to make the telescope as smooth as desired.

Where did you buy yours from? I think that like me you are in the UK. I looked for embossed FRP but the places I found didn’t offer small-ish sections like and/or charged a lot for postage. Eg here…

https://www.whitecladding.co.uk/product/white-embossed-frp-fibreglass-wall-protection-panel/

The smallest size is £55.99. But add VAT and “economy” postage of £30 the total comes to £103.

I had a hard day at work and had to do the “cooking”, well, in charge of a BBQ. So, decided that I was too tired even though the sku and moon did look good. 

However, to me the ball in your picture looks more like a turnip. But maybe that’s just me! 

On 30/05/2023 at 07:43, markse68 said:

Excellent find Peter. My hunch is the anodising is harder than the melamine surface of formica but like moonlight focusers, the softer foundation material (alu) will lead to eventual wear esp with abrasive dust. BUT it’s cheap enough to replace and easier to work with so looks to be most excellent! 👍 If I do ever get round to building my 12” for which i have a beautiful mirror in a box, I’ll give this a go- thank you. Nice bit of bling too

Mark

I’ve used my Dob with this for a few sessions now and it definitely works well. Stiction, and by that I mean the holding force (static friction) that must be overcome before the bearing begins to move, is excellent. Eg - it’s enough to hold on target when changing eyepiece etc. But when I want to move the OTA it moves smoothly without any, or very minimal, jerk or overshot - even at high magnification and/or when the Dob has been stationary for a while. 

I’m doing to add some of this to my altitude bearings which still have Teflon pads on a textured ABS sheet. This works OK, but there’s some stiction, especially at high powers. I also want the feel in all directions to feel identical as possible.

As you point out the aluminium/anodised surface will wear (everything does) overtime. Will wait and see how long this takes and when it makes a noticeable difference. When using other materials I have found that temperature, especially cold, can make a difference to stiction. But I haven’t yet had a cold night to try this. 

On 30/05/2023 at 06:49, NGC 1502 said:

Over many years I’ve made several Dob mounts and modified others.  I think experimenting is key because it’s hard to predict how well it will work in practice, especially (as mentioned) at high power.

There’s so many factors involved and not just in the choice of materials.  I once made a Dob mount for a Skywatcher 10” Newtonian tube assembly bought secondhand. It was ok at low power but iffy at over 100x. After lots of frustrating DIY eventually the problem was revealed. The plywood base of the mount was not completely flat.  As it turned on the ground board at times it was ok but at other times it was not, like trying to push something uphill or downhill.

Let me explain further “pushing uphill” :-  As the mount is rotated you are also trying to lift the rocker box and tube assembly a tiny bit higher from the ground.  At other times the opposite occurs.  Stiction will vary greatly from no stiction to obvious and frustrating stiction.  

I’m hoping the above makes sense.  Although the construction of a Dob mount looks simple in design don’t allow that to make you casual. Make everything exactly square and flat, rigid as possible.  Make it less of a hassle to take apart if necessary by not using glue in the joints, just screws.

The “stucco embossed aluminium sheet” certainly looks the part- and as it works so well rejoice👍

Ed.

I agree that experimenting is key. And I enjoy experimenting, so it adds to the fun. And for me it’s something to do during the summer months too, when it’s obviously not completely dark at night and visual opportunities limited.

Getting plywood, or any sheet wood, nice and flat without warps can be a task. It’s better with the more expensive wood but I’ve found that even then there can be warps. One reason that when I made my Dob base I went to the supplier and inspected each section of 18mm plywood that they had. Then only purchased sections that were warp free. Mind, I think that they thought that I had a case of OCD  But a few sheets were getting to a banana like stage. Buying online must be pot luck and something to avoid.

3 hours ago, RobertI said:

Thanks for the details, sounds like it works pretty well. M44 and M81 are about 50 degrees apart so that’s pretty good accuracy across a fairly big slew. I’m guessing that the larger the slew the less accurate it becomes without re-synching to something. Just curious to understand how this all works. As the Starsense app effectively auto re-synchs itself every time you slew to something, no manual re-synching is required, but Starsense does have its limitations (eg, bright moon) and obviously can’t be used during the day. Its interesting to understand the difference between the two approaches though - I might try both apps side by side one day as an experiment. 

Yes, the larger the slew then the less accurate it becomes without syncing to something. Although if I spent a lot of time on a target then accuracy will also decrease. I’ve learnt, if possible, to sync as I go along. Very occasionally, I think it’s only happened to me twice in a year, it was really inaccurate from the start. I found switching the phone on/off sorted that! 

Trying both apps side by side would be interesting. I don’t think that anyone has done that.

18 hours ago, RobertI said:

I also have PS Align Pro and was just going to start using it for push to before I was seduced by Starsense. Just out of interest, do you use the ‘hop from nearest star’ feature or do you find it works accurately without? 

I find it works accurately without. ie I almost always use PushTo. 

Generally if I sync on something that’s not too far away from the target it’ll have the target within my 9x50 RACI. Eg I was observing the sun in white light this morning. Then, at about 1pm, I took a look at Venus. To do this I did a sync on the Sun then a PushTo Venus. This was all that was needed to have Venus well within my RACI. I’ve really enjoyed observing Venus during daylight and have been watching its phase change since February. A first for me. Venus at night is virtually impossible from my back garden as by then it’s behind trees and houses. 

To get a target within a low power eyepiece - for me that’s 25mm which on my 200p Dob gives x48 - I generally need to sync on 3 stars/objects to guarantee success. However, often I’m lazy and will align & sync as I go along. Eg earlier in the year when observing the Orion Nebula. Then decided to look at the Beehive. Before moving I synced on the Orion Nebula, then (as it was easy and not far off) synced on Betelgeuse. PushTo the Beehive had it in my 25mm eyepiece. After looking at the Beehive I synced on it and did a PushTo M81, which again had M81 within my 25mm. A nudge and I had m81 & M82 in the save FOV. 

On 27/05/2023 at 13:03, bosun21 said:

The PS align is better than the Skeye by being more accurate in target acquisition however I found the Starsense to be superior to them all.

I’ve no doubt that Starsense is superior to PS Align Pro but then it should be as PS Align costs peanuts - £2.99. I’ve used PS Align Pro for 14 months and it has never failed to find a target, so it’s hard to justify getting anything else. Although if someone gifted me a Starsense unit I’d happily take it off their hands

I also use PS Align to accurately find planets during the day. Recently Venus but Jupiter, Saturn and Mars too. 

38 minutes ago, PeterStudz said:

 

What I’m trying to point out is get the right bearing material and you do/can have both.

When I’m slewing through a large number of degrees moving friction becomes less. Then when I stop it stays where it is. When at rest there’s enough friction to keep it there in order to do things like change eyepiece or attach a camera. When I start to move it moves smoothly without jerking and without overshoot. 

I might be mistaken but my understanding is that stiction is the holding force that must be overcome before the bearing can begin to move.

Just now, PeterStudz said:

Yep, that’s it. And it’s possible to get ideal stiction on a Dob without a break/knob. 

1 minute ago, cajen2 said:

No confusion from me: "Stiction (noun) - the friction which tends to prevent stationary surfaces from being set in motion".

Yep, that’s it. And it’s possible to get ideal stiction without a break/knob. 

2 hours ago, Stu said:

It is a single shot, but these days I use Live mode on my iPhone and most of the time it picks that sharpest frame from the little sequence. Works really well on the Moon. On this one I think I picked a different frame manually.

This was at about 20.45, so it was still light and Venus was reasonably high. I have picked it up earlier before. I still found that the wedge helped. Like you I see dimming towards the terminator and some other very slight variations but far from convincing so far to me.

I’ve used Live Mode but on the Moon & Sun, but thinking about it I haven’t on any of the planets.

Live Mode is handy and I don’t think that many people realise. Although it won’t handle RAW. However, having played around with RAW I’m not convinced it’s that much better on these kind of iPhone images. 

15 hours ago, Whistlin Bob said:

Welcome to the world of playing with dobs!

While playing with kit & DIY isn’t for everyone it’s one thing about DOBs that I like. When I first got into this I had assumed that like most stuff these days a telescope would be largely stuck, glued and welded shut. It’s refreshing that these things can be completely taken to bits and put back together with simple tools. Plus the amount that you can DIY. It’s great 😊 

6 minutes ago, cajen2 said:

Well, as you say, each to his own. But I like the idea that I can alter stiction to suit me, not rely on an average.

But for me it’s not average - it’s perfect, that’s what I want! I also think that there’s some confusion or misunderstanding of “stiction”. 

32 minutes ago, cajen2 said:

I don't understand the problem with Lazy Susan Bearings. My StellaLyra 8" had one but crucially, with a knob to vary the stiction. For normal scanning of the heavens, the knob was loose or slightly tightened (ensuring easy movement) and while changing EPs on a target, I'd tighten it. Simple job and for me, it worked perfectly.

It’s personal, so one isn’t better or worse than the other. But for me (when I tried a lazy Suzan) your description of having to use a knob or similar to vary stiction was one of the things that annoyed me. With the setup I have now there’s no need to fiddle with any knob! 

On 23/05/2023 at 23:09, bosun21 said:

I’ll be definitely giving it a go in the near future. I have the Celestron Starsense unit already fitted so target acquisition is easy enough for me. I’ll put a bit more time in pointing the platform North and ensuring it’s level. I’m looking forward to it.

I guess if using  Starsense you’ll need to take your phone out in order to take images? If I think that I’m going to image I’ll sometimes setup the phone in the adaptor + eyepiece attached and ready to use as one unit right the start. Then all I need to do is swap out eyepieces. Saves having to fiddle and attach the phone to adaptor, then adapter/phone to eyepiece… all  in the dark.

To check tracking you can use the phone attached to an eyepiece/telescope. Then point at a bright star and use the grid in the camera app and watch if it stays more or less still. If the star moves then adjust motor speed. You can also take a 30 sec exposure with the camera, then, If there’s no too minimal star trailing, you are fine.

Some time ago I also polar aligned my platform as in the link below. Go to the end of the article. Then marked the position on my patio. The process is a faff so more of a one off. But it can show if you need to adjust, say the south bearing, ever so slightly. Also an activity to do on these far to light summer nights  

http://www.astrosurf.com/aheijkoop/Equipment/EqPlatfor2.htm

Is this a single shot image? And not a frame from a video. I’ve only managed anything out of Venus via taking video.

And have you tried observing Venus during the day? Then I don’t  need any filters. And the advantage of daytime is that Venus is obviously higher in the sky so potentially less impact from our atmosphere. When observing during night time it’s certainly very bright and I certainly need a filter.

I can see dimming towards the terminator but I haven’t been convinced about any other shading from the clouds on Venus. Sometimes I think that I can see something subtle but far from far from 100% sure it’s real and not just down to the seeing. 

57 minutes ago, Cornelius Varley said:

At this point it might be worth mentioning that the OP hasn't visited SGL since March 26, so might you might be talking to yourselves.

This is true and certainly a comment worth making. However, I’ve found and followed discussions like this without myself making a comment and found them very useful. Eg @bosun21 torch suggestion is one I’ve previously discovered on this site and used myself. It’s just one of the things that makes this site so useful and why I keep coming back. 

7 hours ago, Louis D said:

Try surfacing the bearing surface with Fiberglass Reinforced Wall Panel in a nubby texture.  It should be glossy to have low friction, but fairly coarse to reduce stiction.  You can run a piece of Teflon across it to get an idea of the feel of it.  I won't lie, it can sound a bit like rumble strips on a highway when rotating the scope, but it works great.

I’m not a fan of the lazy Susan bearing type things. And I tried to find the above wall panel stuff in the UK without luck. But this -  stucco embossed aluminium - worked really well for me. Cheap too. I paid £13 for a 50cm (20 inch) square from a local sheet metal supplier. Lager sections are available. And easy to cut with tin snips.

Works well for altitude bearing plus Teflon too. 

2 hours ago, westmarch said:

@noodlehat  Just saw this post by @PeterStudz that may allow you to use an app as a cheap alternative to your setting circle.  Since the iPhone is finding its alt/az independent of the platform, this might work with an Eq platform.

John

Yes, I use it regularly with my EQ platform.
 

In fact I’ve literally just come in after observing the sun in white light. Then, using my phone with the goto feature in the app PS Align Pro, syncing on the sun, I was able to find Venus in daylight. Of course it’ll work at night just as well and you can use your Dob plus EQ platform in the normal way. 

14 hours ago, Kon said:

These look excellent especially doing the full processing on the mobile.

Thanks! Amongst other things I find doing all the processing on the phone a nice challenge.  Now it’s summer and taking inspiration from you, I  might just give the International Space Station a go. I was literally just outside putting our bunnies to bed and it made  a bright pass overhead. And a few days ago, when I was setting up, it unexpectedly came overhead. I didn’t have an eyepiece to hand but I could easily track it in the finder. Maybe it’s giving me a sign! 😃

8 hours ago, bosun21 said:

Great captures Peter. You have given me the inspiration to try this with my 12” dobsonian and EQ platform. I was going to go directly to a dedicated Astro camera and laptop but I will probably try this method as I already have the required phone and holder etc. Thank you.

Definitely worth a go and I’ve found it a lot of fun. Although the app can align without any tracking the whole thing was easier and worked better on the EQ platform. For a start there’s no need to nudge/move back to the target in order to do another capture. As your  target stays in the FOV for longer you can take longer exposures. And for some reason the app alignment was more reliable on the platform. So that it can align the app does need some relatively bright stars in your FOV. And I only aligned my platform for visual - level with a spirit level, orientating north with a compass.

For editing images  I’ve found the app WaveletCam useful plus Lightroom (just the free version). Occasionally SnapSeed too.