PeterStudz

Got up at 3am just to take a look at Saturn. Nice rising crescent moon too but behind trees. Skywatcher 200p Dob in Southampton. 

Despite Saturn still being relatively low it was easy to make out shading and subtle banding to the north and thin but prominent ring shadow. The rings are much more side on compared to the last time I saw Saturn in the winter. I couldn’t make out the Cassini Division but it’s going to need decent seeing this year. And two moons (I assume Titan & Rhea) were easy to see even at 4am as it was getting light. 

Packed up to the dawn chorus. Back to bed for a couple of hours. Definitely worth the effort!

1 hour ago, bosun21 said:

Guess I just need to get longer arms from somewhere then🤔.

If you decide to stick it down to the whole tube there are various ways of going about it. Not sure what’s best and it might depend on the size of your OTA. 

I went with a suggestion on here (it was for the same OTA) which was to flock in 3 stages - top, bottom & finally middle section. Top & bottom were relatively easy. Doing and reaching the middle was a little awkward but when doing it you felt like you were on the home straight. And there was also the benefit of gaining experience on the easier sections.

And I know that some recommend doing it using long strips of flocking material. I can see how that would work. 

5 hours ago, Ratlet said:

There is something satisfying about looking in the tube and seeing nothing apart from blackness and the mirror.

I agree here. There’s a lot to be said about feeling good with the job that you’ve done. 

The Skywatcher 200p that I flocked was a restoration. The inside had some white staining/marks (see pics) that however hard I tried to clean would not come off. It kind of made sense to flock the whole thing. The result is nice to look at and if nothing else satisfying! And I found it very easy, the extra cost minimal, so why not? While I was at it I even flocked the inside of the focuser draw-tube (literally a 2 min job as I had it all apart anyway), painted the outside of the draw-tube and back/edge of the secondary. 

Whatever I did certainly improved contrast on the planets and light scatter when viewing bright objects like the moon. It’s minimal but with planetary you need every bit of help with colour contrast that you can get. Mind, I’m not convinced that it made any noticeable difference on DSO, but I’m in Bortle 7 so DSO aren’t great at the best of times. 

I can’t say if doing the whole OTA makes any difference compared to flocking just a small area. But would I do similar again when I get another Dob? As it turned out so well for me I certainly would!

I did my 8” Dob last year and managed to do it wrinkle free. But wrinkles aren’t going to matter and you could argue that they might actually help. Eg some telescopes have a series of ridges inside & down the tube, to help knock out any reflections

22 hours ago, Kon said:

I am not sure  it matters which eyepiece but for transits you are not going to get much detail anyways. Your focusing is spot on as well. Your first attempt, really? You can't tell! Well done again.

You are probably correct. Although when I’ve taken images of the full solar disc the 15mm gives better contrast and details of sunspots. So, I was thinking more of that rather than the ISS and transit.

Focusing is made more difficult with the phone attached to the eyepiece. And in daylight there’s a lot of screen glare. Personally (there are other ways), I find it easier to first get a rough focus, then do a AE/AF lock (allows you to lock the focus and exposure values). Then fine tune using the telescope  focuser to the now locked focus of the  camera. Maybe take a guest shot/video to make sure it’s spot on. This also prevents the phone trying to hunt for focus which is especially annoying in the middle of a video!

It’s certainly fun and if I get the chance I’ll give it another go. A lunar transit would obviously be worth a go but will need to wait a while for that.

48 minutes ago, Kon said:

That's fantastic and ISS next to the sun spot is awesome. The shape is really nicely defined. That's the best mobile phone transit I have seen. I have been imaging ISS for the last 3 years and a transit has eluded me.

Thanks! I was very surprised that it all came together at the first attempt. Definitely lucky in that respect. 

However, I was a bit miffed that I had to use my StarGuider 25mm. I have a few StarGuiders which I like, but this isn’t my favourite and I keep meaning to upgrade it.  I have the 15mm which I find good (just right for pictures of full disc solar) but with iPhone video it cropped the edges. 25mm being a bit too zoomed out. 18mm might just be about perfect and possibly give a better result that the 25mm. Maybe not. Conditions/seeing were also good.

And I was pleasantly surprised that you can recognise the shape of the ISS. For a first go I would have been happy with more of a fizzy blob. That’s if I ever get the chance of another go! 

ISS Photobombs the Sun 07/06/23

Well, my first attempt at capturing an ISS solar transit. And surprisingly everything fitted together - the transit didn’t drift far from the initial calculations, the sky was actually clear, it was during the late afternoon when I wasn’t working, or on the school run etc. I used the excellent ISS Transit Finder website…

https://transit-finder.com

First video in real time - it’s fast! - about 1sec to cross the disc. I’d started the video about 1 minute before. That 60 seconds seemed to go on for an age. Surprisingly exciting to see the ISS flash past the screen.  

Second video slowed to 1/8 full speed.

Image created using every 5 frames. Took a while to work out how to do this on the phone. Might give it another go to see if I can do better.

Image of ISS and sunspot.

Captured from home in Southampton. SkyWatcher 200p Dob on DIY EQ platform. DIY solar filter using Baader AstroSolar Safety Film. BST StarGuider 25mm. iPhone 14 Pro held to the eyepiece using a no-brand smartphone adapter. Video shot using the stock camera app set to 4K at 60fps. All editing done on the phone using the stock camera app, iMovie, Snapseed & Lightroom. 

8 minutes ago, John said:

It looks like an iron pyrite nodule. Someone asked the Natural History Museum a question about a similar specimen a few years back:

NaturePlus: Coprolite? (nhm.ac.uk)

They thought theirs might be fossilised dinosaur poo !

 

 

Yes, it’s a pyrite nodule. Relatively common in chalk. I use to go searching for them (when fossil hunting) when I was a kid in some of the chalk pits near/on the Surrey Downs.

Interesting discussion. I’ve only been observing Venus for the first time this year. The vast majority of the time during daylight - after dark and  from my garden Venus rapidly disappears behind a damn great tree and then rooftops. I’ve also been recording the phase with my smartphone which has been fun.

I was looking yesterday afternoon (Sunday 4th) using my 200p Dob. Seeing on Venus was the best I’ve had and for the first time I thought that maybe, just maybe, I could make out some clouds details. But like  @John  - I was not convinced that I could see anything "real".

What I saw could be summed up by what @Franklin succinctly describes above as “hints of shadows branching away from the terminator”. But were these caused by clouds or something else? My daughter, who has better eyes than me, could also make them out and she described these well enough without me saying anything. I through that I could also see some extremely subtle mottling on the clouds too. But again, not sure it was anything “real”.

When I looked at and started to process a couple of my smartphone videos (incidentally, I’d annoyingly overexposed theses a tad) you can just make out the “shadows branching away from the terminator” that we’d seen visually. But what are they? I’m not sure.

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.