Mike Harlow

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  • in reply to: Nova Vul 2021 #584477
    Mike Harlow
    Participant

    Just had a quick look at the object through the objective prism and as Robin has shown above there are strong H alpha and beta emission lines.

    in reply to: Mirror re-coating #584462
    Mike Harlow
    Participant

    Thanks for the info Robin, very interesting.

    Looks like going back to silver is the best option for the UV!!!

    Mike.

    in reply to: Mirror re-coating #584459
    Mike Harlow
    Participant

    Hi Bill,

    I had a Hi-Lux coating put on my 12 inch mirror by Orion Optics a few years ago and it is still in good condition.  I haven’t examined it recent for pinholes but it still looks uniformly bright despite several years outside in the observatory. So I’m happy with it.

    One thing that may be an issue is the reflectivity in the UV and IR, outside the ‘visible’ range.  When doing spectroscopy I get the impression I’m not seeing as far into the UV or IR ends as I did when using just a plane old aluminium coating.  I haven’t quantified this and it’s not really a significant problem but maybe something to investigate?  I did contact Orion Optics to ask what the reflectivity was beyond their specified range of 400-700nm but the customer service person didn’t seem to understand the question(!).  

    Mike.

    in reply to: Nova in Hercules #584358
    Mike Harlow
    Participant

    Yes, much fainter than I was hoping for but still bright enough for a low resolution spectrum:

    Very broad hydrogen lines dominated by H alpha emission.

    Mike.

    [26cm, 3 degree objective prism on 30cm F/6.8 astrograph.  6 x 15 seconds at ~23:30BST 13th June 2021]

    in reply to: Starlink Flares? #584308
    Mike Harlow
    Participant

    Thanks Nick, very nice video! Picks up the fact that some satellites were on slightly different paths (slightly north or south) as Stan noted earlier.

    Mike.

    in reply to: Starlink Flares? #584305
    Mike Harlow
    Participant

    Thanks Stan et. al. good to see you got some images of the event.  I should have realised that meteor cameras would be picking these things up all the time.

    I’m reliably informed that the pass included Starlink 2261 which passed through Delphinus at 01:07 from my site in Suffolk.

    Thanks again for everyone’s feedback; they are interesting events to witness if somewhat disturbing for deep sky imagers.

    Mike.

    in reply to: Nova Cas 2021 #584282
    Mike Harlow
    Participant

    Thanks Hugh, that’s a really interesting summary of recent changes…I’m glad I was seeing something real!  It will be fascinating to see what it does next…

    Mike.

    in reply to: Nova Cas 2021 #584279
    Mike Harlow
    Participant

    I’m still taking spectra of the nova whenever possible and the latest one from last night seems to suggest that the helium lines are coming back.  Can anyone confirm this?  I’m no expert on novae but I can’t remember seeing one like this before.  Can anyone explain what it’s doing and has this sort of behaviour been seen before? And it appears to be creeping up in magnitude again!

    Thanks,

    Mike.

    in reply to: Nova Cas 2021 #584201
    Mike Harlow
    Participant

    Ideal conditions last night to try for a higher res. spectrum; no wind and low humidity.  The result is on my members page and shows some nice detail at the blue end of the spectrum.

    Mike.

    in reply to: Nova Cas 2021 #584197
    Mike Harlow
    Participant

    An image from 23:30UT last night (10th)…nova at centre of 25 x 25 arc minute frame, north up. It may seem like overkill to image a mag 5.3 nova with a 30cm telescope (!) but I’ll be able to follow it as it fades back to mag 18,19 or less with the same set-up.  Should make a nice sequence…maybe even an animation…!?

    I did look but couldn’t see it naked-eye. But it was very nice through binoculars and the 4 inch F/5 finderscope on the main telescope. 

    Mike.

    in reply to: Nova Cas 2021 #584190
    Mike Harlow
    Participant

    Hi Hugh,

    Wow…that’s a really nice spectrum!  I’m impressed that you got such a nice result from the .jpg without even seeing the .fts file. Anyway, it does show one thing…I need to get to grips with some spectroscopy software to produce some more useful results.

    You’re right that the red end is saturated as it’s difficult to get the exposure right to show both ends correctly exposed, especially for red objects. 

    Some background on the prism.  It was instrument no. 179 in the BAA instrument collection and I took it out on loan in 2012.  Thanks to Bob Marriott for organising the loan and even delivering it in person!  I purchased it from the BAA a few years back when the instrument collection was finally sold off.  Apparently it has been used by some famous names in the past including Mike Hendrie and David Sinden.  But most notably it was used in the 1980s and 1990s by Maurice Gavin for much of his pioneering work on spectroscopy with film and CCDs.  This work was published in the BAA Journal in 1996:  ‘Stellar spectroscopy with CCDs-some preliminary results’.  J. Br. Astron. Assoc. 106(1) 1996, p11-15.

    It may be old technology but as you’ve shown it can still produce useful spectra. And given it’s history I feel I should keep using it as long as I can.

    Thanks for taking the time to analyse my spectrum…I must make more effort!

    Mike.

    in reply to: Nova Cas 2021 #584187
    Mike Harlow
    Participant

    Luckily I was out last night (7th) taking another spectrum of the nova but with slightly better resolution.  As soon as I found the field in the finderscope it was obvious the nova had brightened significantly. The spectrum now shows very well defined P-Cygni features on most of the emission lines.

    Astronomer’s telegram ATel14614 gives a nice update on the nova’s evolution. 

    in reply to: C/2020 F3 (NEOWISE) #582774
    Mike Harlow
    Participant

    Hi Robin,

    I did try a transmission grating spectrum this morning just for fun. Maybe shows the image of the tail in sodium light???  A bit faint but I’ll try again next time I get the chance.  Larger image on my members page,

    Mike.

    Details: Thor labs 300l/mm transmission grating in front of 55mm lens on un-modified Canon 550D DSLR.

    in reply to: Nova Cas 2021 #584155
    Mike Harlow
    Participant

    Hi Hugh,

    Thanks for the info, that’s very useful.

    And I must say your animations of the changing spectrum are fascinating to watch.  Really excellent work and thanks for sharing them on your members page.

    Mike.

    in reply to: Nova Cas 2021 #584145
    Mike Harlow
    Participant

    Hi Robin,

    Thanks for the information, that’s very useful,

    Mike.

    in reply to: Nova Cas 2021 #584143
    Mike Harlow
    Participant

    Hi Hugh,

    A link to the BAA database would be useful for those of us who haven’t used it.  That’s what I like about ARAS, all the spectra are easily visible to anyone…plus they are stored in a database for scientific research by the specialists.

    And that’s a very nice spectrum…a full sized version on your members page would be good.

    Thanks,

    Mike.

    in reply to: Nova Cas 2021 #584140
    Mike Harlow
    Participant

    A recent Astronomer’s telegram, ATel 14577, details changes in the spectrum with the emergence of iron lines.  Lots of spectra on the ARAS web site show these lines developing with He I lines fading.

    The He I lines labelled in my low res spectrum from 23rd April may actually be Fe II instead… More spectra planned when the skies clear again…

    in reply to: SN 2021hpr #584106
    Mike Harlow
    Participant

    I’ve attached my recent objective prism spectrum not because it shows anything new but to illustrate a trick used for line identification. (Taken on 12th April 2021).

    I usually image and take spectra through an Astrodon luminance filter which has a sharp cut-off at 700nm.  The result is that all spectra cut-off at that wavelength giving an internal reference on all the spectra in the field. Coupled with the dispersion equation for the prism this enables reasonable estimates for line positions. In the spectrum of SN2021hpr the first absorption below 700nm is the Si II line as shown nicely in Kevin Gurney’s spectrum (of another type-Ia SN) and those above.

    I can’t claim any originality here, this was a trick used by professional astronomers conducting objective prism surveys in the 1960s, 70s and 80s.  Some of the photographic plates used had sharp spectral cut-offs imprinting a known wavelength on their spectra.  And when you have a Schmidt photographic plate with 1000s of spectra on it that’s really useful!

    in reply to: Nova Cas 2021 #583996
    Mike Harlow
    Participant

    Taking a closer look at my image from 19th March I just got the Bubble nebula at the edge of the field. Image on my members page: V1405 Cas and the Bubble nebula.

    Mike.

    in reply to: Nova Cas 2021 #583968
    Mike Harlow
    Participant

    Quick look low resolution spectrum.  Reveals a bright continuum with strong hydrogen emission lines and some other as yet unidentified emission lines. Field is 12 x 6 arc minutes and conveniently includes an ‘ordinary’ A-type star spectrum for comparison(!) with hydrogen absorption lines. Taken with a 26cm, 3 degree objective prism on a 12inch F/3.6 astrograph.  24 x 20 seconds. 19th March 2021 at ~21:00GMT.

Viewing 20 posts - 1 through 20 (of 47 total)