Adam J

6 minutes ago, Mark2022 said:

I've been looking at these boxes and then I find that, to power the box itself, I need a Pegasus power supply!! £59!!! I'm getting a little tired of these bloody rip offs everywhere you look within Astro circles! But people pay it!! So they'll keep charging it!

I am sure that any 12 - 13.8 volt supply will do just fine. 

Adam 

1 hour ago, Figgis said:

Dear All.

                As I rarely use this Mount now, I thought I might busy myself during the short nights by stripping it down and changing the Bearings.....I've seen several references to Bearing Size & Reference Numbers, which has left me in the Dark as to what the correct sizes are.....Anyone swapped theirs and can remember what they used?

You simply measure the bearing, one number will be the inside diameter another the outside diameter and the final one the depth of the bearing. 

Then search google for those measurements and select a nice shielded ceramic one. 

Adam 

SO...to bring this back onto topic, there are reports that people who have more recently opened the mount up found glue like residue already on and around the adjustment screw.

So it appears that Skywatcher may have taken note and added a step to the build process to prevent the screw from becoming loose over time. 

See purple substance below on and around the thread. Essentially the same solution as what I applied to my mount. 

Credit:  Challenger 75 on cloudy nights 

https://www.cloudynights.com/topic/808906-star-adventurer-gti/page-21

Adam

1 hour ago, OK Apricot said:

Due to a for sale thread on here, I noticed that this flattener has an M63x1 thread which is the same as the focuser on my 61EDPH II. I'm curious as to whether this element would work with this scope, considering it's designed for F6 and the EDPH is natively F/5.5. It's a nice thought that I could shoot at its native focal length opening up some different framing options as compared to the usual 0.8x reducer/flattener. 

Cheers. 

My worry would be that you might have issues reaching focus as the 0.8x flattener that comes with that scope is very long. If you have a large amount of outward focus travel then you may get away with it though while maintaining the required spacing for the Planostar flattener. 

Maybe someone else has done something similar though. 

Adam

1 hour ago, GTom said:

Same question here for Baader's LRGB-set: older stock says CCD optimized, no haze, no reflections etc, new stock is "cmos optimized". Any practical difference between the two?

Not sure but what I can tell you is that my CCD optimised set work just fine with my CMOS camera.....so not much space for improvement. 

Although if the chart is anything to go by the newer set is cutting at 400nm instead of 380nm on the blue filter.....would have thought that would be more dependent on the correction of your camera but it might indicate higher blue / violet sensitivity in CMOS in comparison to CCD....though i am not sure that is true. 

My experience though is that is you are poorly corrected in Blue 400nm wont cut it you need to be at more like 420nm to see a significant improvement. 

Adam

22 minutes ago, Adam J said:

Are you sure you have those the right way around as I would have expected the teal colour from the tri-band and the green from the duel band. 

That tri-band filter is not what I would select for an emission nebula. 

Adam 

Actually while that ZWO is technically a duel band filter its very wide in the OIII and so is not a true duel narrow band filter. I would get something like the L-Extreme instead. It looks to be almost 40nm wide. 

1 hour ago, AstroMuni said:

Hi all,

I had a chance to do a quick comparison between these two filters and thought I would share it here.

Both sets of images (30 x 60s) taken on the same night with setup of SW130pds + ASI533MC Pro with gain 240, offset 70 and -5deg. Stacked + Background extraction done in Siril followed by Autostretch.

With Antlia Triband https://www.firstlightoptics.com/antlia-filters/antlia-triband-rgb-ultra-filter.html

With ZWO dual band https://www.firstlightoptics.com/narrowband/zwo-2-duo-band-dual-narrowband-filter.html

 

Are you sure you have those the right way around as I would have expected the teal colour from the tri-band and the green from the duel band. 

That tri-band filter is not what I would select for an emission nebula. For the 533 i would grab a 1.25. 

Adam 

2 minutes ago, AstroMuni said:

It was spinning around but when I attached stop ring it grabbed it.

I think i need a photo as I am a little confused as to what you are trying to describe. As far as i remember the stop ring does not interact with the filter thread. 

2 minutes ago, AstroMuni said:

There is a thread but for some strange reason I couldnt attach the filter without adding the stop ring which meant that the whole assembly did not fit into the focuser tube.

It should go on. Do you mean that the thread locks up before its fully engaged? 

1 hour ago, AstroMuni said:

Resurrecting this thread, as I would like to get the Antlia Triband filter which unfortunately comes only in 2" form. Is there a way to connect this to the ASI533MC pro without using a filter drawer? I also use the Baader CC so need to bear that in mind.

Does it thread onto the badder coma corrector, seem to remember that mine had a thread on the scope side of it. 

As an aside though I don't like tri band filters duel band is the way to go. 

Adam 

On 08/07/2023 at 09:51, Elp said:

Managed to try it with my C6 w HS. It's quite a relief not having counterweights as the whole thing could be comfortably lifted via one hand under the tripod and carrying it next to the body for support rather than needing two hands for stability with a gem.

Guiding was a bit of an issue, seeing wasn't too bad but I couldn't get it below an average value of 1.2-1.5 RMS, tried short 0.5 to 3s guide exposures, it worked best at 1s. Looking at the graph the Dec was also working better than the Ra which you would not expect. Best average went down to around 0.8 RMS total but quickly went back up again. Subs weren't too bad so I guess will see next time, also need to try other imaging rigs to see the result.

PA was around 45 arcsec east heavy.

Slewing speed is quite fast which is good for when testing E W payload balance.

Typical guide graph from last session:

 

Also the small 5.5 x 2.5mm male to 5.5 x 2.1mm female plugs for the 12v in weren't very good, although there was no issue whilst imaging, when I was manually adjusting the scope it kept turning the power on and off at the slightest touch. Now going to try a short converter extension cable instead.

I always expect Dec to work better than RA as if you are well aligned the Dec should not even need to move lol. 

On 14/06/2023 at 01:31, ONIKKINEN said:

I think you can use any 12V DC power supply as long as its rated for at least 3A output. So 5A would be more than good enough.

I have a power in/out readout screen in my 12V power bank, so the guess of 1 amp in use comes from that. Its not super accurate, but its not far off either.

I know that my ASI1600MM pro only draws 1A when cooling ot -20c. So 3A supply is reasonable as you should not run a supply at full rated draw continually anyway. If you are going to power the entire rig and not just the camera 5A is then a reasonable choice. 

Adam 

18 hours ago, bottletopburly said:

Thanks for sharing your experience, I thought about player one as I’m thinking of maybe going to 533mm at some point after reading your comment regarding about paying shipping that puts me off tbh there’s no middle ground it’s either working or there is an issue, no we will fix replace but you’ll have to pay shipping that puts me off and also why they need a uk agent , I will probably stick to zwo knowing if an issue arises and if  I buy from Flo they’ll sort it .

Yes they need a UK distributor and retailer. Until then it's not attractive to me. 

Adam

33 minutes ago, Peds said:

Or you could get a 2.7nm filter (it's +0.5nm/-0.1nm). There must also be an undisclosed margin of error for the 3nm pros.

In any case, the filter bandpass is not the only interesting metric. The fact that it transmits more Ha, OIII, SII - which is what we're interested in as imagers - shouldn't be overlooked.

In the worst case scenario, a 3.3nm filter bandpass isn't so bad...

 

Yes for the 3nm I would be shocked if its not also a similar margin, placing all these filters in overlapping error bands.

Its deminishing returns but with an element of gambling lol

Adam

18 hours ago, Calzune said:

Soon I will buy the 2600mm pro camera and for that I need filters (36mm).  I have until now used Antlia 3 nm filter with my 1600mm pro.
(I live in a bort 6 zone)

I need to buy a whole new filterset because I have 31 mm currently, that's why I'm asking. 

Is it worth spending a little extra for the 2.8 nm filter? Or should I just go with the "safer" option --> 3 nm?
How are the Antlia LRGB filter?

Its 2.8nm  +or- 0.5nm so you could end up with a 3.3nm filter.....

Adam

3 hours ago, 900SL said:

Zwo state that input voltage is 12V to 15V on their cooled cameras.

Anybody ran theirs on 15V? Reason I ask is that I have a USB C PD powerbank that can supply 15V 3A ( but not 12V )

I have a 15volt power supply, measured it before using it and it came out at 16.2volts. I would leave a margin for error....

Adam

1 hour ago, zernikepolynomial said:

 

Adam, I have watched that video multiple times in the past, and I have actually myself derived his equation for calculating optimal exposure time based on a desired relative noise level and the cameras noise characteristics, as well as light pollution. If you run the calculation yourself, you will see that going from 1.38e to 1.5e results in an increase of (1.5/1.38)^2 = 1.18 times the original exposure length to reach the same noise target (18% longer). That is significant, and it does warrant investigation. Now, will that be noticeable in the images? It depends. If your doing long exposure astrophotography (fewer exposures, but longer) then no.  If you are doing short exposure astrophotography, then it can make a significant difference.  Also, if your signal is very weak, it can be VERY noticeable. All that information is in the video that you yourself have referenced.

So what I will say is that you have now posted a large amount of information that you did not include in your original posts.

I had also worked out the 18% but the thing is in most cases people over expose anyway and so unless you are keeping your exposure as short as possible you will probably never notice as you are likely to be above the required exposure in either case for the read noise difference to have no effect on a stacked image. For example when you look on astrobin most people are taking 300s or similar exposures, way longer than required and producing fantastic images. So unless you are wanting to use 20second exposures and moving to 24second exposures is a problem for you, you are just not going to notice it.  Also important to remember that's 18% more sub exposure not 18% more total exposure. 

The main thing that drives my exposure time is not trying to get the shortest possible exposures for my read noise and sky conditions but more that I don't want to be dealing with 1000s of subs. 

My guess is that playerone have taken 20 cameras tested them and presented the best results. Sensor to sensor variation is a real thing. 

Can you post a dark frame? The general issue with this type of sensor measurement is that the stats can be effected by a small number of bad pixels that in practice calibrate out, although I don't know the exact method used by Dr Glover to potentially reject these. Perhaps you could find someone with camera and the same sensor to make a comparison with. 

You may have said above but have you tried a different capture program?

Try not to dwell on it and be too disappointed. It's still going to take great images in the right hands. My experience is that one of the biggest factors in end image quality is the imager themselves. 

Adam

1 hour ago, ONIKKINEN said:

I think you are being a bit unfair here. There is nothing wrong with sharpcap itself and just advicing to "take some images with it" is just plain silly when OP has a genuine worry here. I would imagine manufacturers also measure camera performance using exposures and measuring the pixel values within (like sharpcap does). These technical specs cant be seen in a single sub frame, at least easily so i really dont think looking at a subframe has any meaningful value here. But the small technical differences can be measured and they can have a real effect in integrations you would not have been able to otherwise see. Im sure you know all this...

Definitely not a panic over nothing. 

Yes his worry is genuine but that doesn't mean he should be worrying about 0.1e of read noise or less by your own estimate. The maths just doesn't support that, 0.1e is not going to have a real effect in integrations especially for long exposure DSO imaging. When I have time I will come back and prove to you with some modelling that 0.1e read noise simply has no effect as the other noise sources are more significant. As above this is certainly withing normal variation from sensor to sensor. 

But if you don't believe me then take a look at Doctor Robin Glover's (yes the man behind sharp cap) presentation on read noise from the 2019 practical astronomy show, it's on you tube. You would spot the back of my head in the audience if you knew where to look. One of his conclusions is that read noise is so low in general in modern sensors that it is no longer a significant contribute to overall signal to noise ratio, so long as your exposures are not crazy short like 10seconds for braud band. 

here is a link: 

39mins and 30 seconds shows the effect of read nose from different cameras on overall signal to noise. 46mins companies 2.5e read noise to 7e read noise and basically even for that huge difference you get the same signal to noise as long as you expose for 120s or more. 

In the end it's just not going to make much difference and it might not even be a real difference at all. Just a difference in how read noise is being calculated. For example outlier handling of hot pixels etc. 

For short exposure stuff like solar system imaging it will matter more. But the IMX533 is more often a DSO camera. 

Adam

On 09/06/2023 at 19:18, nfotis said:

 

(wish there was an IMX294-size sensor with the IMX571 technology)

 

 

IMX472 would be the current closest candidate but I would think it's only a matter of time really. 

Adam

5 hours ago, zernikepolynomial said:

While they did offer to take the camera back, Player One decided to go against their 30 day policy and somehow simultaneously claimed it was not a true "performance failure" to pay for shipping and still weird enough to take it back. Shipping costs back to their factory are way too much, and I would rather save for another camera than pay for that. Not to mention the risk of sending anything back to china just disappearing if it takes too long. 

 

You might have better luck, but anyone else should wait until you see more performance results before buying from them. My results may in fact be the true average, which is not much better than a typical 533mc camera from other manufacturers when taking into account how it responds to gain. Mine must be over 1.5e at unity gain (125), 16k full well. Can hit up to 1.5e at gain 150, 12k full well. My sweet spot will probably be at 1.38e at gain 200, 7k full well, or maybe even whatever I can get down to 4k full well. It will just be a balance of not overexposing with my fast newtonian operating at f3.75, while taking the shortest exposures possible due to its weight.

So first thing first. Are you aware that ZWO and Player One also ( unless I am mistaken) do not use Sharpcap for their chart generation. So what you have is three different measurement methods in play here. I think playerone have chosen a more generous method of measurement as your figures are not far from the ZWO figures for the ASI533mc pro. You say 1.38e at gain 200 7k full well. ZWO are saying about 1.3e at gain 200 and 5k full well. So a little lower but at what looks like slightly higher relative gain. Now these difference between Normal read noise and LRN mode are small as things go at unity gain you are talking about 0.11e between the two modes. I would expect the read noise variability from sensor to sensor to be larger than that tiny difference. If it was my camera the difference between 1.38 and 1.5 would not bother me at all and you won't visually detect it in your results that's for sure. 

But as above I think the bigger issue is you are comparing apples and oranges if you are looking at those charts and expecting them to perfectly match results from sharp cap. 

So I think you should stop testing the sensor in sharpcap and take some images with it. There are many other sources of noise beyond read noise that everyone forgets about and added together make your little differences in read noise insignificant in terms of total noise. Just expose very slightly longer if it is really eating away at you and your will have negated the effect anyway. 

This is a panic over nothing. Go take some images. 🙂

Adam

13 hours ago, bomberbaz said:

Hello all.

I have recently acquired a 650 FL reflector and I already have a camera which was actually purchased to be used with another scope which didn't work out.

So problem being is it is the ASI 183MM, px size is 2.4 which potentially leads to oversampling at 0.75"/px

I have been offered a loan camera, the ASI 174MM, px 5.86 which gives under sampling at 1.86.

So clearly neither are ideal but rather than rush out and buy a new camera, I want to test out the rest of the setup for balancing, tracking etc, you get the drift before doing so.

Given the above, I am swinging towards the 174 given most of what I do is from a heavily light polluted garden but anyone else have any pointers as to which may be best suited to test out until I am ready to make a decision on a more permanent solution.

Since when is 1.86 under-sampled and why don't you just software bin the 183 in processing?

Adam

FRA300 would be my choice. Spot diagram says it all. 

2 hours ago, andrew s said:

Just consider where the principle plane is in a compound telescope. It is not always one of the lenes or mirrors! 

This illustrates how effective focal length of the whole system is defined using marginal rays. 

Regards Andrew 

 

 

Yes but the point is that it is a physical measurement from one point to another that changes when you add a filter. 

12 hours ago, andrew s said:

To be pedantic a plane parallel glass element doesn't change the focal length it shifts the focal plane.

Regards Andrew 

Depends on if your frame of reference is the mechanical path length or the optical path length. As we are talking about spacers and the physical position of focus changing we are talking about the mechanical path length between the objective and focus and that has changed. 

In fact both have changed, the thing that has stayed the same is the F-ratio of the system as the angle of the light cone is the same. Its a bit like how some corrector designs with also change the position of focus and hence the mechanical path length. 

However, looking at the definition on Wikipedia the focal length is defined as the physical distance between the focal plane and the principal plane of the optical system and so I am going to go ahead and say that the focal length has by this definition been changed by the addition of a parallel optical surface.  

Now if you want to talk about the focal length of the objective, thats the same, but we are talking about the focal length of the entire optical system including filters and corrector and cover-glass etc..

Adam  

Oh this one again. The mistake everyone makes is thinking that you need to move the sensor by adjusting back focus so that the sensor lays on the new focal plane as dictated by the added glass. This thinking leads to confusion. What you actually need to do is ensure that the focal reducer is on the correct part of the light cone when the sensor is in focus i.e you don't want the change in focal length to result in the position of the corrector changing. 

Hence the thing to remember is that the focal length of the scope is slightly extended by the introduction of the filter (and sensor cover glass that everyone forgets to add) so to keep the corrector in the same place as it is without that glass you need to add that difference in focal length onto the back focus quoted for the corrector. That distance normally being 1/3rd of the thickness of all flat glass elements in the light path between corrector and sensor. 

If none of that made sense stop thinking about it and just add 1/3rd the glass width to the back focus. You don't need to understand it for it to work. 

Adam