dan_adi

If weight is no problem then go ahead. Polar alignment is easy

I guess looking at the spectra of the star should give this information

Made a little progress ... Here we have a database with H alpha fluxes: http://vizier.cds.unistra.fr/viz-bin/VizieR-3?-source=J/MNRAS/431/2/fluxes Also the article that discusses the theory: https://academic.oup.com/mnras/article/431/1/2/1036908 On pg. 12 in the pdf "...with the exception of McCullough et al. (2001) whodetermined a flux for Abell 36 of F(Hα) = 2.8 × 10−11 erg cm−2 s−1,which is 28 per cent lower than our own determination of 3.9 × 10−11 erg cm−2 s−1."If I look up Abell 36 in their database I find a logF = -10.41 mW/m^2 Playing with the code: import numpy as np from scipy.integrate import simps # Given logFlux in mW/m² logFlux_mW_per_m2 = -10.41 # Convert logFlux to regular flux in mW/m² flux_mW_per_m2 = 10 ** logFlux_mW_per_m2 # Load filter transmission data from file (assuming two columns: wavelength, transmission) filter_data = np.loadtxt('H-alpha-3nm_2.txt') wavelengths = filter_data[:, 0] # Wavelengths in Ångströms transmission_values = filter_data[:, 1] # Filter transmission values # Interpolate the filter transmission data to match the flux wavelengths (if needed) # Assuming the filter and flux data have matching wavelengths # Calculate the product of flux and filter transmission flux_times_transmission = flux_mW_per_m2 * transmission_values # Integrate the product over the wavelength range to get erg/s/cm² erg_per_s_per_cm2 = simps(flux_times_transmission, wavelengths) # Convert the result to erg/s/cm²/Å by dividing by the bandwidth (in Ångströms) erg_per_s_per_cm2_per_Angstrom = erg_per_s_per_cm2 / 30 #bandwidth_Angstrom print("Flux in erg/s/cm²/Å:", erg_per_s_per_cm2_per_Angstrom) The result is : Flux in erg/s/cm²/Å: 3.90462998411593e-11 So I think this is the way to convert the vizier flux data to flux density in H-alpha since the values is identical to the one in the article. In order to compute the counts we divide this flux density by the photon energy at 656.3 nm. Now all I need is to compute the sky brightness from a H-alpha fits file in ASTAP, the result being in mag/arcsec^2. Then convert that mag to h-alpha flux (based on the article data), and finally, hopefully compute a correct exposure time in narrowband. This is much harder than BVRI imaging, all because there is no standard "magnitude" system for narrowband

If you have a H alpha sub and some calibration files for it, load them in ASTAP please and post the sky brightness value. Thanks a million

Cosmology_calculator · Streamlit (go.ro) Enter a redshift in the calculator and it will compute everything. The maximum redshift is 1089, this takes you very close to the big bang. Look at the numbers and the space time plot. The plot was easier for me to understand than raw numbers, although it was a total headache to code the graph, namely the light path So, if you enter a cosmological redshift (z) of 1089: the universes age at that z was 0 the look back time or light travel time was 13.78 billion years during the light travel time , the universe expanded very fast. Space can expand at a speed greater than the speed of light, the objects within space are confined to c, space can do what it wants. the proper distance today to the edge is 45.2 billion light-years. Multiply this by 2 to get the diameter ~ 90 billion light-years !! This creates some confusion ---> For objects in our cosmic backyard you can safely say 'if a star is 4 light years away that means the light from it travelled 4 years at c', but for objects far far away (bigger z) this statement no longer is true! The lookback time is time, not distance The plot is more interesting than the numbers. You can see different horizons and the light path through space-time. If you know the z of a galaxy you can enter the value and analyse its evolution through space-time. You can even see when or if it crossed the event horizon :). If it crossed the event horizon, the light that it emits now will never reach us again!, and it will slowly fade in our telescopes until sometime in the future, disappear.

Lately I was reviewing the math for my exposure time calculator. Everything works out fine for broad-band imaging, but I am stuck on narrowband. With broad-band, in Vega - Mag system every Mag/Flux is normalized to Vega. If we take a random 18 V Mag star we can simply compute the flux as, F = 10^(-0.4 * m) * F0, where F0 is the 0 point flux for the V band. Further we divide the flux to the photon energy and we get the counts. But what about a H-alpha emission nebula? We don't have H-Alpha magnitudes, and we don't have 0 point fluxes. I did find an example in the HST handbook, see the attached screenshot. In the example the flux is provided, but how? Do I search Vizier and get the flux for the object? After I find the flux don't I have to normalized it somehow?

Great scope! Also great to see a fellow amateur astronomer from the same region

I use USB to Ethernet devices. The signal is send through the local area network and I keep the control computer Inside. This way I had 0 issues with connectivity for the last couple of years. A pegasus ultimate coupled with 1 or 2 of these works reliably https://www.silextechnology.com/connectivity-solutions/device-connectivity/ds-600

That is strange ... my text file looks like yours but my Name/SourceID doesn't start with 3 but 1 Gaia Data Release 2 (Gaia collaboration et al., 2018, 1,692,919,135 sources) Name;RA(deg);Dec(deg);PixelX;PixelY;SourceID;RPmag;Gmag;BPmag;Parallax;RadialVelocity;Radius;Luminosity 1635992831624107008;250.016699;65.791918;133.377575;7815.995706;1635992831624107008;17.7037;18.1383;18.3954;0.0374;;;

Hello, I used PIs Image Annotation script with GAIA DR2 catalogue on my image. I get quite a few objects annotated, somewhere around 3000 of them. Luckily the script also generates a txt file with the objects. The object ID id like: 1635992831624107008 When I go to Vizier->GAIA DR2 catalogue and enter the IDs provided by PI I don't get a return, the object is not found. I must be doing something wrong on the vizier website These are the first IDs from the list if anyone knows how to search for them in Vizier: 1635992831624107008 1635992831624107776 1635992870279767552 1635993248235648896 1635993278300714752 1635993209581371392 Also the link to vizier: Vizier

Thank you for the kind words. Indeed my inspiration was from Mortens work. He did it with a slightly bigger scope and better skies, but after doing the math I saw it was possible with an 8 inch scope too. I continued gathering data these last few days, and I am at 130-ish hours in Luminance. So I am approaching the 200 h total time. I have refined the calibration process and got rid of some residual dust motes and other artefacts. As a first step I sorted the bias and dark frames according to year, by introducing another keyword for WBPP (I didn't know I can use multiple keywords for WBPP). This way each set of darks and biases can be assigned for the specific season. The resulting Luminance master is much cleaner now. For the colour masters, making a synthetic flat did a wonderful job. Once I introduced a new keyword, I had to rename all fits files, around 3000 of them :)) and that was no fun, but necessary. Another hiccup was that StarXterminator was removing the arcs and small galaxies in the centre, so I couldn't process the cluster core separately from the stars. I've found I can spare the centre region by applying the GAME script mask and invert it. It is still a work in progress, most likely I will finish next galaxy season, depending on how the weather cooperates. I am aiming at 200 hours for the Luminance and maybe a bit more colour wouldn't hurt either. Overall, I'll end up with a 300 hour exposure time picture, kind of an amateur deep field of that region :). I am confident the image can be much improved as I learn more and more about processing in PI.

I played around with PI and got a little bit better result. This is a crop at native resolution without drizzle.

Thanks, I still need to practice processing ... the image can be improved

Sure

I've manage to capture some RGB data for the Abell 2218 project. The R was replaced with NIR because I already had the data from last year. Specs: Scope: CFF 8 inch refractor Mount: Mesu 200 Astrodon L filter: 100 hours, bin 1, -10C, 300 sec Astrodon B filter: 20 hours, bin 1, -10C, 300 sec Astrodon G filter:20 hours, bin 1, -10C, 300 sec Astrodon NIR filter:27 hours, bin 1, -10C, 900 sec Original image scale: 0.93"/pixel Data was drizzled 2x Software: Prism Observatory Control v.11. Pixinsight 1.8.9-1 Total exposure time: 167 hours during 2021,2022,2023. This is my first astro LRGB image so my processing skills are at sub - newb level. I think are need more color data, probably because luminance has 100 hours vs 20 hours per RGB .... I added 3 images: The whole wide field shot. Center crop Magnitude vs log10(SNR) chart, to see how deep I could go. Identifiable arcs: ARC 359 (R mag = 21.4), ARC 384 (R mag=21.68), ARC 289 (R mag = 21.67), ARC 730 (R mag =21.93) Quick reference source: The system of arcs in the cluster of galaxies Abell 2218 Magnitude reach at 167 hours: object with mag=25.148 SNR=3.482 Some overall impressions: I think I need more colour data. Probably the amount of hours in Luminance washes out the colours ... Definitely need to take my time to learn processing! Probably the longest exposure done with an 8 inch scope of this region? the best image with a 12 inch scope I found on Astrobin by Morten C. : Abell2218 - 67 hours Thanks for looking! Final_LRGB-2.tif Final_LRGB.tif

I use Prism v.11 to control everything in the obsy. It is a one time fee, and to my knowledge the only software that controls everything for an observatory. You only need this software and nothing else. It's been around since 1995 mostly for professional use, and really don't know why it isn't more popular. I had no issues with it, upgrades are free. This is their latest version: https://www.prism-astro.com/en/produit/prism-v11-english-version/

Also I've updated the website. A download link for the windows standalone app can be found there too. the link to the web app: https://clearskies.go.ro

This is normal behavior. I also image with a refractor and I need to refocus during the night. The change in temperature induces a change in focus position. You will have to refocus. In my case, I got an Optec Leo focuser with an external temperature probe. The probe is fixed to the scope. Then I simply made a liniar regression model between temperature and focus position. For my setup the correlation coefficient R^2=0.92. So I have a 92% correlation between focus position and scope temperature. Then I introduce the slope coefficient in my software and I can get away with not focusing during the night. Sometimes I simply use temperature compensation sometimes I refocus

Get a refund and buy a Mesu mount.

Interesting idea. It should work but the cost will be prohibitive. You will need 3 cameras, and possibly some way to fine tune the focus for each camera separately, ideally with a electronic focuser. For a while I used a on axis guider from innovation foresight that uses a dicroic mirror to split the light into visible and near infrared. With the main focuser I would focus the visible spectrum and with a helical manual focuser the NIR. As you can imagine the manual focuser ia not so precise. Also the weight would increase. Also such a device would eat up a lot of backfocus. My ONAG if I recall correctly needed around 60 mm. So overall, 3 cameras, 3 focusers, backfocus problems, more weight...

Finally had the time to make this a proper windows application. Install the app. Run it as Administrator. The app prints the results to a pdf file and opens it with your default pdf viewer. Written in python and free to use. Attached is the setup.exe and some pics. ETCSetup.exe

I think good seeing is bellow 1 arc second. In our backyards, as amateurs, we rarely have good seeing to take advantage of bigger aperture. You can see in our own pics that the refractor and the C11 have the same median FWHM. The only thing that more aperture brings in this case, is reaching the desired SNR faster (bigger mirror, more photons). Anyways .... I do prefer refractors because they are close to perfection and plug and play, but if I were to have < 1 arc second skies, I would surely get a Planewave CDK or a ASA Newt

Had a simliar experience. In my case, Meade 12 inch SCT vs CFF 8 inch apo. Imagine your TOA being 8 inch! It will make the C11 look like a toy even on galaxies. Enjoy you TOA!

In theory yes! But in practice ... have you worked with a SCT? They are by far the worse imaging platforms out there. I almost gave up on the hobby because I started imaging with a SCT. Some points regarding my SCT: I could not efficiently prevent dew, I could not focus reliably with the stock focuser, the main mirror moved while slewing, mount modelling was worse , and I could go on ... but you get the point. My solution to my SCT problem was a refractor. In my particular case a 8 inch CFF refractor. After I took a glance on a few subs from the refractor compared to the SCT, I kid you not, I threw the SCT in the garbage bin.

I'm curious if you tried going more towards the science part of the hobby. Astrophotography is harder than exoplanet detection or spectroscopy or photometry of asteroids etc. Sometimes I wonder if I wouldn't be more enthusiastic about confirming an exoplanet myself rather than imaging m42. After I finish my abell 2218 lensing adventure, I'll explore the science part. I have a feeling I'll more into it. Anyways food for thought...