[Robin Leadbeater]

Here are typical spectra of M5iii in red (R Lyr) and A0v in blue (Vega) with a typical sensor QE curve (black) overlaid, first at equal V magnitude and then with the correct relative magnitudes assuming RR Lyr Vmag =4.0.

R Lyr is ~ as bright as Vega in the I band but should still look significantly fainter integrated over the response of an unfiltered image. (Unless perhaps close to the horizon where atmospheric extinction would reduce the difference)

Cheers
Robin

Attachments:

1. 

   Vega_RLyr_same_Vmag_QE_overlay.png
   

2. 

   vega_RLyr_fluxscaled_QE_overlay.png
   

[Robin Leadbeater]

Here it is in a 1 sec exposure with my finder last night. (Fuzzy with this unfiltered fast achromat due to the high flux in the IR)

Cheers
Robin

Attachments:

1. 

   TCrB_20240410_010953.png
   

[Robin Leadbeater]

Robin Leadbeater wrote:

today

tomorrow ! I am often told I dont know what day of the week it is, there is the evidence !

[Robin Leadbeater]

Another bit of eclipse viewing stupidity. Apparently Amazon US are refunding people (using the dealers’ money) who bought SeestarS50 smart scopes because it might be dangerous to view the sun through it as the solar filter does not comply with the AAS filter advice !
https://www.cloudynights.com/topic/917434-seestar-warning-email/

Hope you have clear skies today over there

[Robin Leadbeater]

Hi John,

This applies when using a standard star spectra eg Pickles in place of an actual measured spectrum and assuming the published spectral type is correct. It depends how accurate you need to be, particularly at the violet end. Francois Teyssier’s Reference Star Finder spreadsheet default setting gives a warning for stars with E(B-V) >0.05 and an alarm >0.1. If you have ISIS you can estimate how much effect it has using the extinction tool on an A0v Pickles spectrum for example. Attached is the error with E(B-V) = 0.1. I suppose you could even correct for the effect, though that is perhaps pushing the use of stars with published classifications but no published spectra a bit far

If you have a star with a known as measured spectrum like the non dereddened MILES stars for example the extinction does not matter in theory of course, though I would avoid using the MILES stars with very high extinction. Although it was I who first advocated the use of MILES stars back in 2011,
http://www.spectro-aras.com/forum/viewtopic.php?f=8&t=191
I have fallen a bit out of love with them as only a few are ideal as reference stars as many are potentially variable.

An alternative is the larger MELCHIORS set of spectra which are at much higher resolution so could also be used with higher resolution spectrographs like the LHIRES for example.
https://www.royer.se/melchiors.html
SpecInti software has a script in its toolbox for extracting them in a form readable by the usual software (note there is a typo, a missing _ in the English version of the script)
http://www.astrosurf.com/buil/specinti2/specINTI_toolbox2_en.pdf
and the STAROS campaign website also has an on line extraction tool
https://search.staros-projects.org/

Cheers
Robin

Attachments:

1. 

   IS_extinction_error.png
   

[Robin Leadbeater]

Brad Schaefer talking enthusiastically about T CrB on BBC World Service “Science In Action”
https://www.bbc.co.uk/sounds/play/w3ct4sdv

Robin

[Robin Leadbeater]

Spectra from 2SPOT and Tom Love now posted in the ARAS forum
http://www.spectro-aras.com/forum/viewtopic.php?p=17753

[Robin Leadbeater]

A spectrum from 2024-03-12 by the 2SPOT team (amateur remote echelle spectrograph in Chile)
http://www.spectro-aras.com/forum/viewtopic.php?t=3122

Very red continuum with very intense, very broad H alpha

[Robin Leadbeater]

Mr Jack Martin wrote:

I have released the collar. When tightened then slackened a fraction of a turn the micrometer is easier to turn.

Then I think you have found the cause of the problem. You can slacken it right off. If it turns freely then, there is no overhaul needed. I find the micrometer setting does not move on its own in normal use but if you want to be 100% sure you can always clamp the locking collar back down after you set it at the wavelength you chose. No need to lock it with the grub screw though. That is really for use in an industrial machinery where the micrometer might be used as a set stop which must stay in position under vibration etc

[Robin Leadbeater]

If the locking collar is engaged and you have the locking screw loosened, it could be worth trying to release it first. (Screw anticlockwise) I just tried mine and when the collar is engaged it can be quite tight to then disengage. Try it with your spare, engaging and disengaging the locking collar does not affect the calibration.

Re lubricant the internet suggests clock oil for micrometers. (not silicone which creeps and could end up on the optics)

[Robin Leadbeater]

If the grub screw was not loose and the locking collar cannot be turned even after loosening the screw it is unlikely that this is the reason that the micrometer had become tight. (Did it suddenly become tight or has it becoming increasingly tight over time). Can you tell from my photos and comparing with the other LHIRES if the collar is engaged or disengaged ?

Other than that I guess it needs an overhaul, removing it, unscrewing the barrel cleaning and re-lubricating. Mine is still fine after 18 years though (I recall you have a remote adjustment, could this have been preloading it causing premature wear?)

[Robin Leadbeater]

Photos with the collar engaged and disengaged

Attachments:

1. 

   lhires_lock_engaged.jpg
   

2. 

   lhires_lock_disengaged.png
   

[Robin Leadbeater]

I just used a Jeweller’s screwdriver but if the grub screw is tight then it seems unlikely that the collar has moved so it probably is not the reason for the micrometer becoming tight. With mine the locking collar is close to the spectrograph body when engaged and there is a definite gap with it disengaged. I will take a couple of photos.

Cheers
Robin

[Robin Leadbeater]

There is a knurled collar at the base of the micrometer held in position with a tiny cross head grub screw which is used to lock the micrometer at a given setting. Has that got tightened down? Mine is fully wound off (anticlockwise) and locked down with the grub screw.

Cheers
Robin

[Robin Leadbeater]

Meanwhile ZTF have “discovered” their second high proper motion star in the past 3 months
https://www.wis-tns.org/object/2023acmv
https://www.wis-tns.org/object/2024dum

Robin

[Robin Leadbeater]

Robin Leadbeater wrote:

That’s odd. According to time on the confirming spectrum on TNS, it was taken a day before the discovery date

Robin

Followed this up with the GOTO team. The date of the spectrum was indeed wrong and is now corrected in TNS

Robin

[Robin Leadbeater]

That’s odd. According to time on the confirming spectrum on TNS, it was taken a day before the discovery date

Robin

[Robin Leadbeater]

Stars with H alpha emission lines (of which there are several in the Pleiades) in a narrow band H alpha filter (where the solar spectrum has a deep absorption) might be interesting.

[Robin Leadbeater]

It is ok, it looks like they are now being diverted to spam

[Robin Leadbeater]

Hi Andy,

I don’t appear to have received any newsletters since no 72 last October. Are they archived anywhere ?

Cheers
Robin

[Author]

Posts