Search Results for 'espin telescope'

[Richard Sargent]

I was also lucky enough to observe the Titan/28 Sgr occultation, including the remarkable central re-brightening referred to above. As Saturn was low down I didn’t think I would be able to see the event from my suburban garden with surrounding houses and trees. So I needed altitude. Did I lug my telescope up a nearby mountain? No I took it to the upstairs front bedroom! See attached picture.

I observed with a 10 inch Newtonian on a Dobsonian mount, and made an audio recording to later time the event details. I recorded the occultation start at 22h 39m 44s and the finish at 22h 44m 59s and sent the results to Andy Hollis who was collating observations for the BAA. I still have his reply letter which noted observations received from about 70 observers.

The second picture attached shows Saturn above the rooftops (brightest object near frame centre). To the right of Saturn I have highlighted 28 Sgr with a couple of lines but it is faint on the picture. After observing the event I didn’t have far to go to get to bed! Yes I’ll be following the final news of the end of Cassini. Would be nice to view Saturn at the time of Cassini’s demise but I think it happens during daylight for us.

Thanks for the reminder Neil of what was a very interesting event.

[Lars Lindhard]

I saw this occultation from my home in Denmark with a friend, and we had to move the telescope around in the garden to find at spot where we could see Saturn. The planet was very low and just over the roof of the next bulding which emitted a lot of heat and made turbulence.

We timed the occultation with my wrist watch and it began about 0h 40m and ended 0h 45m on the 4th of July Danish summer time. (GMT +2)

We did not report it to anyone, but we had a great time.

[Martin Mobberley]

Hello Eric,

>Is the spider and mirror mounting centrally placed and the mirror offset applied when gluing the secondary mirror to the flat?<

Yes. See the pic of the front end of Mike Sidonio’s Orion Optics AG12 which clearly shows the arrangement. This is roughly f/4, so an extreme case:        

http://www.pbase.com/strongmanmike2002/image/132998032

To be honest, at f/6 you won’t notice a lot of difference, assuming the secondary is big enough, especially on such a modest imaging circle. Minor vignetting can be flat-fielded out.

Place your eye at the distance where your CCD sensor will be. Does the secondary show you the whole of the primary with a bit to spare? If so, fine.

For planets, assuming the telescope is collimated and cooled down, seeing conditions are the biggest factor by far. Everything else is pretty trivial!

Martin

[Eric Watkins]

I’m just in the process of re-building an 16″ F6 Newtonian reflector.

With regards to the secondary mirror offset.

Is the spider and mirror mounting centrally placed and the mirror offset applied when  gluing the secondary mirror to the flat?

If I’m using the telescope for deep sky work imaging  and planetary imaging where the imaging area is relatively small,

i.e. 12mm x 15mm for the deep sky work, is the offset that important?

Thanks, Eric

[Martin Mobberley]

I was just watching my downloaded video of Richard Miles’ presentation and, around 35 minutes in, I was surprised to hear Richard asking me a question, if I was watching the video…..! The question relates to Roy Panther’s comet discovery of Xmas Day 1980 and my activity that night. That was indeed the night that I first used my 14-inch AE reflector in Newtonian mode,
having acquired it a few weeks earlier. I had used it in Cassegrain mode prior to that and, just 2 evenings earlier, took a photo of the Mare Crisium which (somehow!) won the Lunar Section photographic competition 6 months later. But Xmas Day 1980 was the first time I used the 14-inch at f/5. It was the first ever night that I attempted sweeping for comets too (I continued for 4 years). I decided that I would start sweeping near epsilon Lyrae and so swung the telescope to that part of the sky, getting the star in the finder. However, being a big equatorial Newt on a high plinth, the eyepiece position, on a ladder, was too uncomfortable, and so I started elsewhere. Little did I know that at the same time Roy Panther was discovering his comet just a degree or two away! In fact, I did not hear about Roy’s discovery until a few days later when I bumped into my former Physics Teacher, Don Woodhouse, in W.H. Smiths in Bury St Edmunds. He told me that he had heard about it on the radio. I’d not seen Don for more than 4 years! It was only months later that it hit me that Roy had found his comet so close to where I had intended starting sweeping on Xmas Day, on my first ever comet sweep. It sent shivers up my spine…literally!

That is spooky enough, but there is another twist. While watching the video of Richard’s talk, as soon as he asked if I was listening we had a MASSIVE isolated lightning strike here (4.10pm) and the power went off.

Are the astronomy Gods trying to send me a message……….?

Martin

[Dawson]

Paul, 

Yes it’s exciting; cloudy in Nottingham and my C11 is at the telescope hospital anyway.

There is another forum thread about the supernova:

https://britastro.org/node/10251

Jeremy and Andy Wilson published a brief article on it also this morning:

https://britastro.org/node/10279

Looking forward to seeing your images of it.

James

[Michael O’Connell]

Thanks Martin.

Would be interesting to put names to the people from the BAA, @ 5:22 in the video, who visited the telescope in 1997. I recognise a couple of the Irish people in attendance.

[MARC TRYPSTEEN]

Hi David,

Many thanks for this friendly welcome. Encouraging enthusiastic people in the exciting world of spectroscopy is my mission and passion. 

Concerning the LR spectral possibilities in case of VV Cep:

Because measurements of Radial velocities, Equivalent Widths and V/R component behavior require real R values >10000 those measurements are not possible with a low or medium resolution spectrograph.

Nevertheless LR recordings are certainly welcome for other purposes. Here come two doublets to the scene: Sodium Na I at 5889.95-5895.92 Å and Potassium K I at 7665 – 7699 Å . Their behavior (IP) and broadening is interesting to study general behavior, observe effects such as reddening, which is important to estimate temperatures & distances. Also the fact that with LR a broader spectral range is visible, which can give insight in the overall behavior of interstellar mass transfer around the  primary eclipse period. So LR spectral recordings are certainly welcome and I encourage interested people to participate! Exposure times for Alpy and LISA between 180 and 300 s will be sufficient, depending on telescope size.

Of course we must keep in mind that spectrographs like the Alpy and LISA are in fact designed especially for the study of faint astronomical objects.

So LR spectra can be uploaded to the database, so we can compare them individually.

Success !

Kind regards,

Marc.

[Jeremy Shears]

That’s a wonderful collection of photos, Mark. Thanks so much for taking them and for posting them online.

I especially liked the nighttime scene on the observing field.

But what a difference a fortnight makes: at Winchester we enjoyed summer temperatures, whereas now we are back to winter. Mind you, the seeing last night was better than I have experienced for a long time, with wonderful views of Jupiter and the GRS though my telescope.

Thanks again for your post,

Jeremy Shears

[Nick James]

Glad you saw it visually Peter. This IC is relatively easy at 8 deg elongation. I have seen Venus at previous conjunctions when the elongation was only 5 deg. You need to be really careful and have a very clear sky. In fact, I also remember trying to see a comet very close to the Sun using one of Denis’ telescopes. We were very careful and one advantage of a dome is that we could block out the Sun so that there was no chance of getting it in the telescope. There is a picture of me doing that somewhere but it is probably best not published for health and safety reasons.

[Peter Carson]

Hi,
A group of us using Andrew Robertson’s Mak-Cass telescope observed Venus at around 15.45hrs yesterday afternoon during an astro camp at Haw Wood farm in Suffolk. Venus was at Inferior Conjunction at the time and I was really suprised how easy it was to see in the telescope set again the pale blue sky.
This was a first for me and something I will remember …thanks Andrew.

[Nick James]

Venus is now a very thin crescent only 11 degrees from the Sun. It reaches its closest angular distance on Saturday when it will be 8 degrees away. This is a video from this afternoon in windy conditions. Don’t try this unless you really know what you are doing. Pointing a telescope anywhere near the Sun can be very dangerous. The picture is a single still from the video. At some point I need to put this through Registax.

The video was shot with a Canon 550D in 640×480 centre crop video mode using a Celestron 6 with a x2 Barlow.

[Grant Privett]

I assume they are worried that a visual observer who happened to be looking down the barrel of a space based LIDAR laser beam might suffer eye damage if looking directly at it through a large telescope using the naked eye. CCDers would not be under threat.

Afterall, even if you were using a laser of a wavelength generally deemed “eye safe” then the light grasp of a 12″ could massively increase the number of photons reaching your eye.

EDIT: Should have read the very end of the survey. They are indeed trying to model the risk to ground observers.

[Richard Miles]

Hi Paul, Peter and Andy,

Trappist-1 and its system of at least 7 planets is fascinating. Yesterday we held our second BAA/UCL exoplanet workshop in London and I finished the day able to read Gillon et al.’s 2017 paper in the journal Nature on the subject. Shame that I am away in Australia and so not able to attend Winchester Weekend.

I think I may have seen Didier Queloz in 1991 when I participated in a French-language workshop at Haute Provence Observatory – I was working in France at that time. The astronomers had plans to build a new high-res spectrometer for the telescope there with a view to detect planets by the radial velocity method: this led to the ELODIE spectrometer in 1993. People thought that they were ambitious at that time. Michel Mayor was also involved and Andre Baranne was the main protagonist at OHP.

As to the question of liquid water: despite not yet measuring its presence directly, we can infer it should exist on one or more of the Trappist-1 planets. H2O is a very common constituent in the universe and almost certainly should exist as a liquid somewhere on one or more of its planets! 

Cheers, Richard

[Chris Dole]

Although I’m far from an expert in these matters, I believe your correct about the converging beam introducing astigmatism. To achieve the correct image scale, these ADCs are usually used behind a Barlow. Would this limit the astigmatism? And does the long resulting focal ratios achieved (>f20) limit the effect? I know that in practice I see improvement in image quality.

The attached image was taken at 17° altitude with a 7″ telescope in July. I can’t replicate this without the ADC without nasty colour fringing.

Chris.

[Peter Carson]

I have a fibreglass dome and walls containing my 315mm reflector on a Paramount. I’ve got a built in damp proof membrane in the floor and the building is completely watertight. However my dome is not draught proof enough to dehumidify the building, I would be dehumidifying the whole world, so I cover the telescope and mount with a cotton sheet and use two 60 watt tubular heaters to warm the air space and raise the dew point. That works most of the time but occasionally when the ambient temperature warms rapidly I do get condensation on the Paramount and sometimes the telescope mirror, so I should really try to cure that. I leave my PC out in the observatory and have only had one failure in about 10 years.

[Nick Hewitt]

Hi Keith

It may be worth a trial of prochlorperazine (Stemetil) to see if your dizziness can be damped down. The only downside of such a trial that I can see is that it can induce drowsiness. Please don’t sue me if you wake up frozen to the telescope after 4 hours use!

[100percent]

Last 2 months I’ve been coping with loss of balance sensory output from my right ear, due to nausea / giddyness not been able to do visual astronomy (night sky and telescope). Expect to adapt eventually but won’t be the same.

Anybody had experience of this problem and how it affected looking up at the night sky and using telescope eyepiece?

Will I have to consider astrophotograpy, looking at images on a computer screen in the future?

Regards

Keith

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[Robin Leadbeater]

If it is a radial velocity effect, the wavelength error should be proportional to the wavelength ie the error should be greater at H alpha than at  H gamma say.  If  as you say the error  is roughly constant in wavelength and given that Demetra is in beta testing, I think I would double checking against a reduction done using ISIS for example in case Demetra is incorrectly measuring the relative positions of lamp and star spectrum for some reason.  

Small absolute calibration offsets between internal lamp and the sky are not uncommon though, due to slight differences in the geometry of the light paths and we are talking a fraction of a pixel here so even if the error persists, it may not be anything connected with the star. (Are you seeing it consistently on any other stars?) Measurements of  the solar spectrum (eg the daylight sky) can be used to quantify these sorts of instrumental offsets. 

Another thing to check is instrument stability. I measured my ALPY to be very stable but changes in temperature and orientation can produce small shifts. Did you measure the lamp spectrum at the same time as the star with the telescope still aimed in that direction? Are lamp spectra reproduceable before and after the observation

Cheers

Robin 

[Andy Wilson]

Hi Jack,

I think Robin and Paul have covered this off well, but I’ll add and re-iterate a few points. It is worth noting that this is the same process as is used for deep sky imaging. The main difference is that you can’t use “sky flats” or just any kind of flat lamp. Instead you need a flat lamp that produces a nice smooth continuous spectrum. The LHIRESIII, ALPY, and LISA all have such a flat lamp built in.

I’ll add that your calibration frames need to be taken at the same CCD temperature, and this should be as cold as possible, whilst ensuring that your CCD can easily maintain this temperature. I find that my SXVR-H694 can hold -20C during the Summer as well as the Winter months.

Best practice is to take of the order of 20+ frames of each type. I was actually taking a new set of darks and bias frames last night. Long overdue as over time the performance of a CCD can change. I try to retake darks and bias frames every 6-12 months. Flats I retake about once a month if I don’t touch the spectrograph. If I change anything on the spectrograph then the flats have to be retaken. This includes focusing the spectrograph collimator lens, but not refocusing the telescope.

I know that John Paraskeva is writing some new calibration routines for BASS. Though MaxImDL has perfectly good calibration routines which work fine for spectroscopy.

Best wishes,

Andy