dan_adi
-
Posts
328 -
Joined
-
Last visited
Content Type
Profiles
Forums
Gallery
Events
Blogs
Posts posted by dan_adi
-
-
Do you guys find meteoblue seeing forecast accurate?
For my location they seem to optimistic, between 1 and 2 arcsec. I use Prism astro software that reports seeing and star FWHM in my subs and the best FWHM I got was 1.9. Usually I have values between 2-3 arcsec.
In Prism the difference between reported seeing and median star FWHM is 0.2 arcsec, this tells me the scope is focused ok. The autoguiding RMS with Mesu 200 is usually 0.2-0.3 arcsec.
So my guess is meteoblue is way to optimistic for my location. I doubt I should get bellow 2 arc sec seeing at sea level..
What is your experience?
-
1 minute ago, Victor Boesen said:
Alright, no worries
I was just curious about the program and wanted to have a look at the code and etc. I don't do imaging so I don't need to code so no need to send it 
The user interface looks very good and straight forward, what library did you use to make it?
Victor
I've searched for some time for something easy, and I came across the Streamlit library for python.
It was way easier than using tkinter.
For filter simulation I used the synphot library published by Space Telescope Institute. These are the guys that look after Hubble and JWST.
Also the astropy library came in handy for automatic conversion of units. This reduces the chance of an error creeping in when working with flux density units, correcting for airmass-extinction etc.
The main equation is fairly simple, you can find different variations of it in the references tab. By far the hardest part was simulating the filters and fluxes, but we are grateful that the pros make their tools freely available.
Astropy is also very cool to work with. For example I made a small bit of code that reads my fits files header, extracts the focuser position and focuser temperature. Then I make a liniar fit between those 2 and get the temperature coefficient. This way I can average the results from a few nights, enter the coefficient in my focuser software and then I only need to focus 1 time during the night with temperature compensation enabled. Cool stuff
-
1
-
-
35 minutes ago, Victor Boesen said:
Looks like a very interesting project!! Do you have a GitHub repository where I could have a look around?
Victor
Hello, I don't have a git hub repository.
I wrote it in python, and used streamlit to make it an web app. Afterwards I used docker to contain the applications and it's dependencies into one place and deployed it.
Streamlit is nice and fast for making WebApps, but the code is re run after a user action, so it took me a couple of days to figure out how to retain the user input values into variables, otherwise every variable is reset and nothing is stored.
I had to use their session_state method to retain values. A little bit weird, but it works.
If you want I can see if I can push the app docker image to their repository, and then you can download the docker image on your PC, and run it locally.
Or I can send you the individual .py files so you can compile it on your own.
-
1
-
-
11 minutes ago, Taraobservatory said:
Hei, this looks interesting.
Stupid question here, but when you say desired SNR? I think I understand this but I better ask for clarification.
What is my desired SNR under 21.78Mag sky ? (Pick a random target) I see that 20 has been put there as a preset but isn't that dependant on the target and sky brightness ? And how does on get to that number?
Kind regards
Roger
Hello, in order to reasonably detect some object you will need a SNR of at least 10. The higher the SNR you want, the higher the exposure time you will need.
The target mag and sky mag will also influence the exposure time. If you have 21.78 mag skies that is really nice. I have 20.4 measured with a sky quality meter.
You choose whatever SNR you want. The higher the SNR the better the detection will be but this also translates into more imaging time.
The project came to be, because I want to detect the gravitational arcs in Abell 2218 with an 8 inch scope and I didn't know how much time I will need on this target. The faintest arc, arc 362 located at 10 billion light years has a mag of 24.5. For a SNR of 20 I will need around 80 hours for Luminance filter with my setup. If I aim for a higher SNR it becomes unpractical... because I have a small aperture scope.
The good news is that I am at 40 ish hours down the road, and if I do an agresive stretch on the image I am beginning to see the faint arc.
I will probably finish next summer, but at least I know it's doable.
-
1
-
-
Hello, the app can be accessed here:
To use the Dark theme, go to the menu option on the upper right corner (the 3 horizontal lines), then click on it, then choose Theme->Dark
Hope you find it useful
-
Hello guys,
It was pretty hard for me to make an individual app for Windows/MAC/Linux, so I rewrote the whole thing as a web application, that I will put on a little Intel Nuc webserver I have at home.
This way anyone will be able to access it regardless of operating system. The best part is that it was easier to make the web app than the standalone application.
Once I have everything in order I will publish the web site address.
Below are some print screens.
-
3
-
-
On 01/07/2022 at 20:20, astronomer2002 said:
Dan,
Thankyou for the information on how you use your mount. I have left the default slew speed at 4 degrees per second, which might be higher than yours. What ramp up/down rate are you using? In the Servocat I have set 3 seconds. I assume you have a Sitech Controller rather than a Servocat, but the parameters ought to be similar. Your guiding figures are the best I have ever heard of.
I have run a number of tests with Gary Myers that indicates there is a varying amount of slippage in both axes during goto's. It isn't predictable, except that the mount always comes up a bit short. This is why I thought the 2000:1 gear ratio may be wrong.
I hear what you say about friction drives, but if goto's cannot get you even close to where you want them to then it would make it frustrating to try and run the mount entirely remotely. Plate solving returned images may help to determine where the mount is pointing, but it does seem a retrograde step to have to do this every time.
Having now spoken to Lucas he tells me that every mount is configured with slightly different gear ratio's which he calculates whilst the mount is on his test rig. This probably explains why he couldn't provide a generic Dat file but general advice that the ratio is around 2000:1
Unfortunately it appears previous owners have not only messed with the software loaded on the mount but also the friction adjustment. After talking to Lucas I agree with him that the best course of action is to get the mount to him to apply any mechanical corrections needed. At the same time he will change the ArgoNavis/Servocat system for a Sitech controller. I had planned to do this myself, but it would be prudent to get him to do it. After it returns, which could be months away due to supply issues, it will be fully operational for the way I (and most other people) want to use it, be fully serviced by Lucas, and so be functionally as good as any Mesu mount out there. I shall then have to consider whether to keep it or move it on. The after affects of Covid have left both my wife and myself with long term issues so plans made when Covid was just getting started are having to change.
Having said the mount potentially may need some mechanical adjustments I have to add that with ArgoNavis and Servocat in unison I always know where the mount is pointing and have been able to use Stellarium to drive it through the ArgoNavis serial interface as well, so not a disastrous situation at all. I guess I was expecting a mount that was over £4K new back in the day, and now running at £6.3K new, to be perfect from day one and exhibit better goto performance than lower cost mounts. One thing that must be said in favour of the Mesu is that the electrical and electronic parts are readily available and that they are supported by the manufacturer who you can talk to. Neither of these points is true for most 10 year old budget mounts.
Ian B
Sorry for the delayed response, haven't checked in for a while.
It's good that mr. Mesu will take the mount and service it. No doubt someone messed with it.
The mount autoguides very well, as well as more expensive mounts, but they are small cut-corners if you will, in order to make the mount more accessible-price wise. For example I didn't like the wire connections and the servos exposed to the elements, a nice aluminium case to cover them would be nice and also protect the sensitive electronics.
Other than that the mount is really good for the high payload.
The only time I see the autoguiding deteriorate to 0.5 " RMS or 0.7" is in windy conditions. But in windy conditions I also have worse seeing, so I don't image anyway in such a night.
In my routine I unpark the mount, so it starts tracking, I focus, then do a platesolve - offset init, then a goto to my target. The target is usually less than 1 arcminute away. I do another platesolve-offset init, goto target, and start autoguiding - imaging. So it would not take more than 2-3 platesolves to get things going.
With regard to remote use, I wrote a little tutorial you can find here on the forum, in order to control the mount through a local area network. It is not hard but it takes a little DIY to make a serial cable and a small investment in a serial server dongle. This is how I control my mount now, and it works reliably, something I cannot say about using USB cables in general ..
I am confident mr. Mesu will get your mount in order.
-
7 hours ago, astronomer2002 said:
Dan,
I have a mi250 with original Gemini 1 controller and motors. Never had any trouble with it. I also have a 2002 AP1200, no unsolved issues and excellent support from AP even though this is also a s/h mount.
I do also have a Mesu 200 which I am struggling with.
I purchased a second hand Mesu 200 after hearing all the good reports about the mount and support for it. I contacted Lucas before the purchase and he assured me he was happy to support the mount. It's carrying capacity is supposed to be higher than the Mi250 and as I wanted to put multiple scopes on the mount I decided to try a Mesu.
A previous owner of the Mesu seems to have changed the configuration of the Servocat and so I am trying to correct it. I lost the ArgoNavis setup during a software upgrade, but that seems to work fine now.
I am now suspicious that the axes are slipping or snagging during goto operations as they always come up short. If I use the hand controller from the Servocat to move the mount until the ArgoNavis display suggests the object is close I invariably see it in the field of view. The ArgoNavis uses its own shaft encoders, of course, so as long as the mount is roughly polar aligned any object can be found in this way.
I have run tests for Gary Myers, the builder of Servocat and the conclusion he has come to is that the rollers are slipping or binding during goto's. This is based on the 2-3 step goto code he wrote for Servocat. Given a goto instruction by the ArgoNavis he says the first course step should drive the mount to within 2-3 degrees of the target. The slew speed is then reduced to run a residual move and if necessary a final step to centre the object. On the test I ran I used the hand controller to move the mount to the object position to prove polar alignment. Then I drove the mount 55 degrees from the object in RA only. Now I issued a goto which should have driven the mount back to the object. Whilst it did alsmost achieve this the first stage only achieved 50% of the move (it stops between stages for a second or two) and according to Gary Myers even on the worst Dobsonians the first stage move goes at least 90% of the way. I believe there is handshaking at the end of each of these move steps between the AN and the Servocat, though I may be wrong.
This may be the issue I am seeing as it explains why after a supposedly successful goto the ArgoNavis suggests the object is still some degrees away. Repeatedly pressing 'goto' does get the object in the field so I am minded to blame the odd performance on the rollers slipping or maybe binding.
There is no sound change during a goto or slew so I have been progressing with setup of the Servocat. The way I understand goto's working is that the AN tells the Servocat how many ticks to drive each axis by. If it is always short then maybe the parameters are wrong. I am now not sure this is the issue but until I have the correct gear ratio and motor encoder resolution in the Servocat I am not 100% sure.
I have been unable to get the original Servocat parameters from Lucas, though he has offered to check out and fix the mount if I take it to him. If he was in this country I would take the mount to him now. Taking it to the Netherlands is a long and expensive commute, which I would have to do twice.
Mesu mounts may be excellent, but a small niggle in one can be extremely difficult to solve, as I am finding out.
Ian B
Friction drive mounts do slip, you can not eliminate it. Well u can but with Renishaw absoulte encoders on RA and DEC...
I usually run my mesu mount with the acceleration and speed at the lowest setting to reduce the slip possibility.
Overall, my guiding RMS is between 0.15" and 0.3" in seeing conditions of about 1.8-3 ".
For gotos I use platesolving.
Did you do your tests with a ccd/cmos camera attached to the scope?
Do you initialize the mount before gotos?
-
5 hours ago, astronomer2002 said:
I have been emailing Lucas for 3 months now - I don't think he has kept the dat files from the Servocat/ArgoNavis versions of the mount. This is why I am asking elsewhere as there are many enthusiastic users out there and I don't think a 10 year old high value mount is that old yet. I have a 20 year old AP1200 and any requests to AP for help get answered immediately. Try getting any support for a 5 year old Chinese made mount - it puts issues with other mounts into perspective.
Ian B
I see from your signature that you use a MI250 mount with Sitech controller? I thought it was a Mesu mount ... my mistake. Did mr.Mesu fit the controller to the mount? Otherwise I don't see how he should have a dat file for that mount. Did you contact Mathis Instruments? Maybe they can help
-
18 hours ago, astronomer2002 said:
Olly,
I connected the Servocat to my PC via a standard USB cable (the Servocat has a USB port on the front)
If you had a copy of the original dat file that Lucas should have included with the mount that would be a good starting point for me.
Here's a screenshot of what I have set up
Have you tried asking mr. Mesu if he has your dat file?
-
Never mind, problem solved .... but nobody uses Prism?? It's a wonderful piece of software for observatory control
-
Hello, anybody using Prism v.10? Have some questions about guiding... The Prism english forum is very silent ..
-
Small update:
If you use Prism v.10 with a Mesu mount, in the Misc tab, Nutate coords and Aberration coords should be unchecked, to avoid correcting twice. Don't know about other software, but the sitech manual states the for TheSkyx these options should also be unchecked. So better to ask SGP, NINA, Stellarium developers how their software report the coordinates, because this will affect pointing.
Since I had the mount I've been running with those options checked. Talk about live and learn 😁
Clear skies
-
7 minutes ago, vlaiv said:
Round stars don't depend on total RMS error.
You can have RMS of 2" and still get round stars (at various image scales).
In order to get round stars - RA and DEC error must be roughly the same, independent and random in nature.
Then I am missing something. So you are saying if I get large guiding errors my eccentricity won't be affected but only FWHM?
-
5 hours ago, pete_l said:
Practice beats theory every single time.
Professionals use exposure time calculators based on theory. The equations are not that hard to compute and give a better estimate than just guessing or practice.
-
On 12/06/2022 at 15:56, Rodd said:
I have been discussing guiding with a friend and we disagree. I wish not to give away my (and his) position by stating my opinion, so a poll is in order. Please read the following and answer the poll question....which is a two part yes/no response. However, if one wishes to elaborate, assign conditions, or make stipulations, one may do so.
Conditions
1) Maximum guiding accuracy of mount is 1.0 total rms (in arcsec)
2) Capacity of mount is unlimited for sake of discussion.
3) Seeing is not the limiting factor
4) Camera is a CCD and the exposure lengths must be at least 10 min for the long focal length F8 system and 3 min for the wider field F4 system (i.e no short ungided subs!)
5) Binning data unnecssary - seeing equals imaging resolution
Questions
A - Would a guide resolution of 1.0 rms be sufficient for imaging at a focal length of 5,000 mm and a resolution of 0.2 arsec/pix?
B - Would a guide resolition of 1.0 rms be sufficient for imaging at a focal lenth of 500 mm and a resiolution of 3.5 arcsec/pix?
EDIT: After realizing that being "sufficient" is a subjective concept, I wish to inform that what I am after here is, will guiding errors of 1.0 rms be visible in the high resolution image? will they but visible in the low resolution image? Some may think that an image is satisfactory while others may not. So I am not talking about image aesthetics, or whether the image is "good enough" for you. I am asking about the visibilty of guiding errors in the image and the general concept of whether this guiding accuracy is sufficient for the imaging systems above. Would it normally be your recommendation to a beginner.
Looking forward to seeing your answers
It's simple really, if one can guide at 1" RMS error with an image scale of 0.2 "/pixel and get good results (round stars), then 10 micron, AP, ASA, Astelco, Planewave etc. would have never existed as mount manufactures.
-
6 hours ago, Taraobservatory said:
Reassuring to say the least. I can honestly not see any noise in your picture. What is your exposure pr sub here? I have never been able to put my gear to proper use yet. The images I have done is no more than max 10subs pr filter at max 300sec for M101 and 180 for the clusters. Not nearly as much time as I actually need. Just waiting to get started again
Clear skies
300 sec per sub, - 10 degrees C. Don't worry, it took me 3-4 years to have a setup that works with minimal effort. By the time I was finished the new gen CMOS sensors came out :))
-
1
-
-
2 minutes ago, Taraobservatory said:
I also have a QHY 268M which I will use with my Esprit 80 for nebula. That has a very low read noise. What other CMOS cams can you recommend. One without amp glow and and large enough pixels for a 1300mm ?
Kind regards
Roger
Small pixels are not really a problem, as you can bin your camera and make larger pixels and optimize you image scale. I guess the new ASI 6200 or 2600 series don't have amp glow. But given your top notch skies the cameras you have will do a great job as is. I use a CCD KAF 16200 sensor and it's ok in Bortle 4. Bellow is a work in progress, about 20 hours worth of subs in luminance with a CCD. I'm ok with it.
-
1
-
-
Given the prices in astro gear this 60 ish pounds is nothing 😄. I did try the cheaper stuff, but as mentioned above, I also found the variation was too great to make precise balance. From the video the gadget seems pretty stable when measuring, also it has a metal case and good cables.
-
3 hours ago, Taraobservatory said:
Indeed,
I have very dark skies and allot of potential to get some good photos. I noticed that my 60 and 120sec exposure of M13 was perfect for stars at least. I also did a another with M92 where I exposed for 180sec where the stars are sharp but not as tight as M13. This leads me to believe that my guiding could be better its but good for my mount (around RMS 0.4 which is great). Its a Skywatcher EQ8r-Pro with a 40kg load. See examples in these links https://www.astrobin.com/53lqze/B/. https://www.astrobin.com/fbphrz/
The reason for the 40kg load is because I have a dual setup which I have now dismantled in favour of single telescope configuration because it gives me more freedom to experiment with different telescopes without having to unload a 40kg rig every time. And hopefully my guiding will improve too if only slightly.
Not sure I gave you full well but it is 31268 from my measure in pixinsight. I believe this also has to be in your calculations ?
Thanks for your help! Really appreciate it
Kind regards
Roger
For example galaxy M33, surface brightness 23 mag/arcsec^2, and a desired SNR of 20 in each band:
Luminance: 1.55 hours
R: 5.38 hours
G:5.72 hours
B: 6.3 hours
For a SNR of 40 in each band:
Luminance: 5.98 hours
R: 21.7 hours
G: 22.6 hours
B: 24.9 hours
As a side note I don't know how the SNR adds in each band, I've had a conversation with Vlaiv some time ago about this, but I could not find some equations in this regard. The conclusion beeing the SNR in each band is not additive, like the final SNR is not the sum of SNR in L + RGB.
In your case I would aim for a SNR of 40 in Luminance, and a SNR of 20 in each RGB, so I would expose for 5.98 hours in Luminance, 5.38, 5.72,6.3 in RGB. Round that to 6 hours in each band, so 24 hours in total exposure time. Hope this gives you an idea about your setup and imaging time.
Another note, for extended objects like galaxies and nebulae, you need the surface brightness for computation, not the simple magnitude. Here is a simple explanation: https://rasc-vancouver.com/2020/08/23/surface-brightness-vs-magnitude/
Clear skies!
-
1
-
-
36 minutes ago, Taraobservatory said:
My goal is to take as short exposures as possible without adding too much noise. I like the stars to be very tight. But I didn't want to miss out on faint details due to noise from my CCD.
Here are some parameters if you dont mind.
Read noise 10,78
Dark current 0.018
Pixel Size 5,3
QE 57%
A 120mm FL 630mm (f5.25)
SQM (Sky brightness) 21.78mag (Bortle 1.4)
What would this look like ?
Kind regards and clear skies
Roger
When I get to my computer I will input your parameters. Don't worry so much about noise, with stacking the signal will "grow" faster than the noise, that is why we stack multiple photos. I also have a CCD with 10 electron read noise and 300 sec exposure for LRGB, in Bortle 4 zone, is a good compromise. If you have such dark skies you can expose for longer, but one limitation would be your mount and guiding performance, wind gust, and also satellite trails and such.
-
1
-
-
It could be run on windows too, with python and the dependencies installed. But first I must run it on my windows machine to check. As a side note the calculator computes the total integration time needed for a desired SNR. The individual subexposure length is not computed. The thing to remember is that the total SNR and total integration time is important. You can reach the desired SNR with lots of small subexposures or fewer longer exposures. What dictates this, is the type of camera you use, CMoS or CCD, your light pollution and read noise.
Clear skies
-
1
-
-
On 14/06/2022 at 20:18, Taraobservatory said:
Hello,
Been through a couple of sites now and watched a few YouTube videos on this topic as it seems to be quite useful. Looks to me as it can save allot of people some head ache and money.
When I am after is a tool that can calculate the optimal exposure for your setup under your particular sky.
I know Sharpcap has a sensor analysis tool which is used to calculate the specifics of your camera, but you also need something to calculate your sky background. Then we can go populate the values in http://www.gibastrosoc.org/sections/astrophotography/optimum-exposures-calculator. This calculator does not talk about CMOS cameras which has Gain and offset etc.. So I believe its a bit outdated (only relevant for CCD). Am I wrong is assuming this ?
A tool that can do all this for you so you dont need to jump back and forth to different calculators and softwares to determine your exposure would be amazing. So if anyone has any idea, please let me know.
The benefits of knowing this could actually save you allot of money. Say you live under Bortle 4 or 5 sky and invest in a have duty mount for better long exposures which is apparently completely useless with a CMOS camera. In fact (if you use LRGB only you MAY not even need to guide as your ideal exposure times can be reduced dramatically with the same result).
Any thoughts and help to understand this better would be welcomed
Cheers
Roger
I had to write my own software for this. Install python, synphot and astropy, then run ETC.py. All files should be in the same folder.
Didn't get a chance to make a standalone app. I'll get to it some time. Tested on IOS and Ubuntu, windows not yet. If you can't compile and run it, PM me and I'll calculate the total exposure time for your target.
Clear skies!
CCD.csv compute.py device.py ETC.py utility.py
-
1
-
-
17 hours ago, petevasey said:
So as a matter of interest, which CFF refractor are you using? Looking at your posts it would appear that you have the 8" f6.5 one? I hadn't spotted them before on the TS site, but now I have - phew - need to win the lottery, but they look amazing!
Cheers,
Peter
Yes the 8 inch f 6.5 one, oiled spaced triplet. Wonderful scope, but now I need some way to disperse clouds all year round:))
I was just curious about the program and wanted to have a look at the code and etc. I don't do imaging so I don't need to code so no need to send it 
The user interface looks very good and straight forward, what library did you use to make it?
Meteoblue seeing accuracy
in Discussions - Software
Posted
I wasn't paying attention on the guiding RMS conversion to FWHM.
Now it makes sense.
I found a formula for estimating final FWHM on the ESO website, can't remember how they dealt with autoguiding RMS, but I'll check and report back.
Thank you Vlaiv